2.3L ('83-'97) 1994 2.3 compression PSI

[bobaloo]

I've done compression tests on my motor and have found #3 cyl. Is somewhat lower than the other three. I'm just wondering what the compression in psi would be for a healthy engine. Maybe the other 3 are low too, but #3 is the worst. Engine has over 300k on the clock and is throwing codes and not running well, but still drive able and getting 23mpg at steady 55mph.
Thanks in advance.

 

[alwaysFlOoReD]

I believe that the lowest should be within 10% of the highest. 130 psi is low. 160 is good.

 

[scotts90ranger]

I don't remember exactly but a good compression would likely be in the 175psi range

Generally if they're within about 15% then it is acceptable... a leak down test would tell you more on health at that "experience level"

 

[rusty ol ranger]

Lowest cylinder should be no more the 20% lower then the highest cylinder.

With 300k anything 125psi+ i would think is acceptable.

Although if #3 is significantly lower then then others you have an issue with that cylinder thats more then likely causing your rough running and possibly even the codes. Youve either got worn rings (least likely), valve issues, or a headgasket issue (most likely id say)

What codes are you getting?

 

[tomw]

If it is 'throwing codes', you ought to try to catch them..... and then reveal to the inquiring minds.
Getting 23mpg at 55 could be a good result, or a poor one, depending on the model, etc.
Not running well is rather vague. Does it stall? poor idle? hesitate upon acceleration? shake and misfire randomly? chug now and again? ...???

 

[bobaloo]

I haven't been able to check out a whole lot due to Michigan weather and I'm in the middle of moving. The one code I get is "insufficient egr flow". Replaced every part of egr system. Still getting the same code. So I don't know. Really bad idle to the point of stalling. No vacuum leaks. I checked out tps voltage did not meet specs, so I installed a new one. Same voltage and idle problem, so I increased idle using the adjustment screw, ( which I know is a big no-no, but I needed the truck). Did major tune up over the summer. I mean major. New plugs, wires, coils, injectors, Idle air solenoid, EGR valve, EGR vacuum control, EGR transducer, TPS, vacuum lines, mass air flow sensor. Disconnected computer cleaned both sides of connectors with electronic cleaner, then cleaned with toothbrush, new timing belt and CPS, all of these things and no difference. I want to check compression and found #3 is more than 10% off put a little oil in cylinder, it was slightly better but still more than 10% off. The only thing I haven't changed is computer, that could be next but I'm thinking the motor is just tired, I know I am. #3 cyl has always been low since I got the truck, but it ran well, now not so good, never burned oil or lost antifreeze, still doesn't. I don't know exact PSI of cylinders because I wrote them down in old garage and lost them in the move. Once I get settled here, I'm gonna pull valve cover and check for stuck valves etc.

 

[Shran]

Did your idle adjustment get the TPS voltage to within specs? Should be around 0.75-1v closed throttle, up to 5v at WOT. Usually this is adjusted by rotating the TPS itself.

Is the EGR valve itself moving? If you apply vacuum to it does it open? Have you hooked up a vacuum gauge to your vacuum tree to watch what it does at idle and while driving? Sometimes that can help narrow things down.

These old 2.3s have some ridiculously irritating idle issues at times. Mine is really bad when the engine is cold. My old one was awful when warm but only sometimes. I have heard that the heads can crack around the valves and that can be one source of idle issues.

 

[RonD]

1994 to 1997 2.3l Lima engine ran 9.4:1 compression ratio(CR)

General rule of thumb is CR x 18 = expected PSI
"18" is psi at sea level(15psi) + 3 for mechanical compression
9.4 x 18 = 169psi

subtract 1 from the 18 for each 2,000ft elevation

But here's the issue, there are at least 3 variables that can lead to lower numbers in all cylinders
All other cylinders must have 0 compression while testing one cylinder, so spark plug out of each cylinder
Battery must be fully charged so starter motor can generate good crank speed
Compression gauge must be calibrated

So the POINT of a compression test is NOT a high/expected number
The point is to see if all cylinders are within 10% of each other which takes variables out of the picture
A lower cylinder will cause misfires, steady or intermittent, depends on how low

In the case of the 2.3l with a timing BELT, it can skip a tooth so all cylinders would be low, under 130psi

 

[bobaloo]

Did your idle adjustment get the TPS voltage to within specs? Should be around 0.75-1v closed throttle, up to 5v at WOT. Usually this is adjusted by rotating the TPS itself.

Is the EGR valve itself moving? If you apply vacuum to it does it open? Have you hooked up a vacuum gauge to your vacuum tree to watch what it does at idle and while driving? Sometimes that can help narrow things down.

These old 2.3s have some ridiculously irritating idle issues at times. Mine is really bad when the engine is cold. My old one was awful when warm but only sometimes. I have heard that the heads can crack around the valves and that can be one source of idle issues.

The voltage at the TPS was not at spec before and after adjusting idle speed screw, but at least engine stayed running. Like I said, I needed it for moving. EGR opens and closes smoothly when vacuum is applied.
I have vacuum gauge in dash, hangs out just under 20 in. No shakey reading, real steady. Hooked up separate gauge at vacuum tree, same out come.

 

[bobaloo]

1994 to 1997 2.3l Lima engine ran 9.4:1 compression ratio(CR)

General rule of thumb is CR x 18 = expected PSI
"18" is psi at sea level(15psi) + 3 for mechanical compression
9.4 x 18 = 169psi

subtract 1 from the 18 for each 2,000ft elevation

But here's the issue, there are at least 3 variables that can lead to lower numbers in all cylinders
All other cylinders must have 0 compression while testing one cylinder, so spark plug out of each cylinder
Battery must be fully charged so starter motor can generate good crank speed
Compression gauge must be calibrated

So the POINT of a compression test is NOT a high/expected number
The point is to see if all cylinders are within 10% of each other which takes variables out of the picture
A lower cylinder will cause misfires, steady or intermittent, depends on how low

In the case of the 2.3l with a timing BELT, it can skip a tooth so all cylinders would be low, under 130psi

I'm at 790ft altitude. Timing belt was the first thing I changed trying to fix bad idle after I checked it with timing light. New belt was installed spot on and checked with timing light & SPOUT disconnected. Reading was almost the same as before.
Old belt had about 80k miles on it, so it was almost time anyway.
I wish I could remember my compression readings, but they are gone. I'd check them again but it's -2F degrees (wind chill) here in beautiful balmy Michigan.
I do remember that #3 was more than 10% lower than others. I guess I'll be tearing things apart more once my garage is free from moving boxes etc.

 

[corerftech]

I will chime in, 1990 with 100k on the engine.
Tests 170/175 with a 180 on one cyl.
Not a spec, just a test outcome on a good tight engine.