Ask GTP About Your Car Problems/General Questions

[Paulie]

Is machining the heads to achieve higher compression considered a dirty and unreliable way of doing it, with risks associated like having a weaker head more prone to cracking? Or is it a legitimate answer to higher compression?

 

[Nicksfix]

Machining the heads will only acquire a slight bump in compression ratio and it will not weaken the head.Milling the block's deck will bump up the compression a bit as well.Obviously if your looking for a big bump in compression ratio,pistons are the way to do it.The CC's of the head have a lot to do with the final compression ratio as well.

 

[niky]

A lot of racers mill the heads a little to bump compression, but like Nicksflix says, pistons are the way to go if you want some real high comp.

Hmm...

Mid-90's Honda automatics aren't the most reliable in the world. Haven't driven one secondhand that didn't feel like it was about to chuck up on the road. The engines, on the other hand, are some of the best there are.

 

[Paulie]

Machining the heads will only acquire a slight bump in compression ratio and it will not weaken the head.Milling the block's deck will bump up the compression a bit as well.Obviously if your looking for a big bump in compression ratio,pistons are the way to do it.The CC's of the head have a lot to do with the final compression ratio as well.

A lot of racers mill the heads a little to bump compression, but like Nicksflix says, pistons are the way to go if you want some real high comp.

Thanks fellas. I just wanted to ask since I need to replace head gaskets, and since the heads will be getting machined anyway I may as well go that bit extra and get slightly higher compression while I'm at it.👍 My brother is getting completely new performance heads for his car which will bump his compression to 11.0:1, just a bit of an off topic note.

 

[niky]

Since it's a general questions thread, nothing is off-topic.

High compression is great... but sometimes it's a pain in the butt... unless you have fuel and ignition tuning, a high-compression set-up will usually require the use of high-octane fuel... and given the load-to-load and station-to-station variance of fuel quality, it's quite possible to damage your engine by feeding it a bad batch of gas.

The tiny bump from milling down the head for an overhaul isn't a cause for concern, though.

Personally, I'd go for a good port and polish, as well as some performance bumpsticks, if they're available for that motor...

 

[Giancarlo]

Are there any dangers or problems that stem from having a port and polish? Reduced fuel economy or something?

 

[Nicksfix]

Are there any dangers or problems that stem from having a port and polish? Reduced fuel economy or something?

That depends on the application of the engine.Most street engines do not need this modification due to the lower to mid range operating RPM.It really comes into play for the high end RPM engines where air / fuel mixture flow is critical.

 

[NissanSkylineN1]

My parents have a '98 Toyota Sienna. We went today for an emissions test and it failed by 2 times the limit. We know the co sensor circuit is malfunctioning. But it failed miserably by 2 times the limit!!! Might there be an additional problem?

 

[niky]

CO or O2? A malfunctioning O2 sensor will royally mess up your air fuel ratios, as the computer adjusts the fuel trim to meet some incorrect, imaginary air-fuel balance in open-loop mode.

Replace it, and you should pass. But you'll have to wait a while for the fuel trims to readjust.

 

[Paulie]

If it's not the 02 sensor it could always be the cat converter.

 

[Giancarlo]

Yeah o2 sensor, cat, air filter, oil change, could be any number of things. Usually if there's a problem with the sensor you'll get a CEL.

 

[niky]

He did mention that they already know it's broken.

 

[Northstar]

Does anyone know how reliable 1997 Dodge Avengers/Mitsubishi Eclipses are?

I found one for 104,000 for $3000 and was wonder if I should bother or not.

 

[Spec M]

Since it's a general questions thread, nothing is off-topic.

High compression is great... but sometimes it's a pain in the butt... unless you have fuel and ignition tuning, a high-compression set-up will usually require the use of high-octane fuel... and given the load-to-load and station-to-station variance of fuel quality, it's quite possible to damage your engine by feeding it a bad batch of gas.

The tiny bump from milling down the head for an overhaul isn't a cause for concern, though.

Personally, I'd go for a good port and polish, as well as some performance bumpsticks, if they're available for that motor...

You can achieve a 12:1 compression with pump gas.
Their's people with higher compression than that running pump gas but it takes extensive ECU tuning (preferably stand alone).

The best and most professional ways to attain high compression is by changing rod length, HC pistons, thinner head gasket and decking the block which should be done by a professional machinist.

Does anyone know how reliable 1997 Dodge Avengers/Mitsubishi Eclipses are?

I found one for 104,000 for $3000 and was wonder if I should bother or not.

Sounds like a decent price and mileage is great.
It depends on what you plan on doing with it though, the older iron block 4G63s are notorious for crankwalk and are not the best under pressure.
The newer aluminum block 4Gs have increased reliability though and not near as many problems.

 

[niky]

That's why I said it would be a pain in the butt unless you can do the tuning for it... maybe even get something like the J&S Safeguard to proactively prevent knock, in tandem with your tunable ECU or piggyback. Was thinking about it, but the design of my engine means no knock... even with ridiculously lean timing and huge ignition advance. Might need it when I go high-comp (after another 50,000 kilometers or so... no hurry), as a friend who changed to the Japanese pistons on his Protege can't use regular at the pumps, anymore...

-

RE: Crankwalk... was kinda thinking that, too... I'd up the budget for an engine rebuild, just in case.

 

[Spec M]

That's why I said it would be a pain in the butt unless you can do the tuning for it...

Oh I see, my bad lol

as a friend who changed to the Japanese pistons on his Protege can't use regular at the pumps, anymore...

Were these just OEM/JDM pistons? Do you know what his compr. was?

 

[niky]

Oh I see, my bad lol

No Problem. I was doing the same thing all last week...

Were these just OEM/JDM pistons? Do you know what his compr. was?

I'm not certain. It's a lowly 10.7:1, I think. But he's already been retuned with those pistons in... I've offered to buy them off of him when he goes turbo.

 

[mafia_boy]

You can achieve a 12:1 compression with pump gas.
Their's people with higher compression than that running pump gas but it takes extensive ECU tuning (preferably stand alone).

The best and most professional ways to attain high compression is by changing rod length, HC pistons, thinner head gasket and decking the block which should be done by a professional machinist.

What octane is in the pump gas that you guys are using there Soprano?? The reason I ask is because the biggest difference for us here in Australia is that we only get 98 Octane as our Ultra Premium Unleaded, otherwise we have to go C16 which makes the car a "little" bit illegal for street use.

I remember with our Isuzu G161 powered Holden Gemini (this was when 96 Octane leaded fuel was around, many years back) that we were running 11:1 compression (stock was just over 9:1) after fitting forged pistons, decking the block and shaving the head .020" (20 thou to the uninitiated) and getting a heap of pinging, even after fiddling around with the ignition advance (you can only advance it so far! ). We had to back off to 10.2:1 with a thicker copper gasket and around 25* of advance.

Paulie, for your car, after the head gaskets are done and the head is machined, do a compression test to find how much it has bumped up....if it's too much you may have to consider running 95 PULP a bit more regularly, but that bit's up to you but I doubt it will bump up that much. Other than that, like Nicksfix & niky said it shouldn't affect the car in any other fashion. As for extra power afterwards (cams, etc.), have you considered any of the C.O.M.E. racing gear?? Especially the 4.2L stroker for the V6??

 

[Paulie]

I should indeed get the compression test done. Maybe the next service in 4-5,000km. I had asked for 10:1 compression, but I don't know if it was done for sure. It does feel a little quicker, but I had extractors put on at the same time to save on labour but without the full exhaust that shouldn't have made a difference. I always run 95 octane fuel, and since the work done I've given it a couple runs from 60-100km/hr (i.e. the span of 2nd gear) and had no problems at all. I haven't done much full throttle other than that because I'm sort of needing to penny pinch right now.

 

[niky]

How high you can go in terms of compression also depends on the design of the engine... Some engines are incredibly resistant to knock... some head designs leave a lot of hot spots, and can start knocking with relatively mild compression.

 

[Murcie_LP640]

Does anyone know how reliable 1997 Dodge Avengers/Mitsubishi Eclipses are?

I found one for 104,000 for $3000 and was wonder if I should bother or not.

Don't bother. Eclipses are infamous for their (lack of) reliability, usually the gearbox is what I've read from the multitudes of questions on none other than Yahoo! Answers. Never owned an Eclipse myself mainly because they weren't sold in Australia. I'm pretty sure there was a good reason for it.

 

[Thatman]

My engine resists knocking well it kinda has too
On to my question, how do I turn the motor on an automatic without the starter? Can i put it in D and push then try starting it? I ask because my Buick has power and everything just that when I go and start it it doesnt crank and sounds "stuck" yet other times it will crank then start...so im thinkin its the crank angle sensor no?

 

[Spec M]

Sounds like you may have to turn it by the crank pulley.
My breaker bar is one of my most valued tools for doing things just like this.
Thats an odd problem and I haven't ran into anything on the field like that before. To make sure the problem is there I would index the crank pulley with a piece of tape or marking it with a stripe with some white out. Then I would try to make the problem reappear while making note of where the marking is on the crank and checking if its in the same position everytime during no start.

 

[Duke]

My engine resists knocking well it kinda has too
On to my question, how do I turn the motor on an automatic without the starter? Can i put it in D and push then try starting it? I ask because my Buick has power and everything just that when I go and start it it doesnt crank and sounds "stuck" yet other times it will crank then start...so im thinkin its the crank angle sensor no?

No, the crank angle sensor is only used in ignition timing and to check for timing belt slippage, really.

It sounds like your starter is going bad, or at least the starter solenoid. My bet is that the starter is beginning to wear out and has dead spots in the armature. If it happens to stop on a dead spot it will not turn over, though it may eventually work its way to a live spot and then throw the engine over. Next time it stops on a live spot and you have no trouble starting it up.

Also, you cannot get the engine in an automatic car to be driven by the wheels, at least not at low speed like in a manual car.

 

[niky]

Yup. The torque converter won't lock up.

 

[Perfect Balance]

Thats an odd problem and I haven't ran into anything on the field like that before.

Really?

How long have you been "in the field"?

 

[Spec M]

Yes "really"

About 2 years now and currently a tech for Toyota/Lexus...

 

[Perfect Balance]

Yes "really"

About 2 years now and currently a tech for Toyota/Lexus...

And you've never heard of a sticking starter or one with dead spots?

The fact that you went though UTI and received ASE certification (according to your sig), and never come across something like this is far more strange than the problem itself. Older cars were notorious for this kind of problem.


EDIT: Or do you work on strictly Toyota/Lexus vehicles only? I haven't ran into any Toyotas with that problem.

 

[Spec M]

The fact that you went though UTI and received ASE certification (according to your sig), and never come across something like this is far more strange than the problem itself. Older cars were notorious for this kind of problem.


EDIT: Or do you work on strictly Toyota/Lexus vehicles only? I haven't ran into any Toyotas with that problem.

How is it strange that I haven't ran across the problem yet? I put emphasis on yet because my work experience has been with with majority cars that have less than 20k on the odo. Me not seeing something on the field doesn't have squat to do with my education. Its the other way around. His situation and diagnosis seemed strange to me because the usual symptoms for a faulty CKP are:

• CEN light
• Engine cranks but won't start
• Engine runs bad/misfires
• Or a tach that doesn't work (most obvious)

He only stated that when he tries to crank, it doesn't crank, it sounds stuck... Do you now understand why that would be weird for the problem to be the CKP?

👍

No, I don't work on Toyota/Lexus "strictly". If you've worked for a dealer before you should know that every used car that comes on the lot has to be inspected, or may need to be written up for general service at least. Besides official business, I just recently replaced all four inner and outer front bearings and races on my Benz and did a water pump and timing job (replaced cam gears, chain, guides and gaskets) on a 2000 Grand Prix with 178k on the odo for a cute chick around the way...

 

[Jetboy.]

No, the crank angle sensor is only used in ignition timing and to check for timing belt slippage, really.

It sounds like your starter is going bad, or at least the starter solenoid. My bet is that the starter is beginning to wear out and has dead spots in the armature. If it happens to stop on a dead spot it will not turn over, though it may eventually work its way to a live spot and then throw the engine over. Next time it stops on a live spot and you have no trouble starting it up.

Could also be the flywheel teeth may be worn enough that it has damaged the bendix gear, and it is getting 'hung up', preventing the starter from actuating. (Something that's happened on my 442 recently.)

Also, you cannot get the engine in an automatic car to be driven by the wheels, at least not at low speed like in a manual car.

It takes around 25 mph in most cases and the risk of damage is serious.



Now, my question:
Car: 1991 Olds Cutlass Calais Quad 442, 2.3L High Output VIN code A

The 442 cuts out below 1200 rpms. The occurrances happen usually from either pulling out from idle, turning onto a road and lugging the car (say taking a left onto a road and keeping third gear around 25 mph). I've just had all the vacuum lines replaced, the car runs on the reccomended premium (91-93 octane out here in Pennsylvania), I replaced the fuel filter, and as far as I remember being told, the fuel pump is putting out good pressure. I also use fuel injection/system cleaners (Not too often about every 2k-3k miles.)

My theory is that either the fuel sending unit is going bad, one of my injectors are failing (But only at this rpm??), or my plugs are going bad (changed last year, Denso's gapped .40). Since it's a Quad 4, there are no plug wires; it's direct coil-over-plug. Anyone else have an idea??


Thanks in advance,
Jetboy