ace322

Here's the deal. My car runs fine when cold but once it warms up the car will bog when I start to accelerate from a stand still and then accelerate normally. Also my vehicle will surge slightly while driving down the road, again this only happens when its warmed up, I can feel like the car is a bit sluggish and is really annoying me. Before you all ask I have already changed the spark plugs, fuel filter, fuel injectors, and I even corrected the timing to 6* BDTC while idling with the EST disconnected. Using my Autoxray diagnostic tool I have the car will knock when I get on the gas but it is adjusting itself and retarding the timing as needed. Even with all this the car still acts up. Luckily it doesn't die on me or anything but I want my car to run smoothly. Any ideas what else it can be?

ace322

Any help would be greatly appreciated

ace322

Also to add to the issue my timing is jumping around from about 14* to 25* while idling. Is this normal or do I have a bad ecm?

John62591

Any info on what engine, and in what car?

How long has this been happening.

Just rebuild the motor, sounds like you have a hastle..

There are tons of things that affect performance from air filters to wires to ugly cars.

You could have a worn fuel pump, spark plug wires, Idle Air Control valve (IAC), vacuum leaks, Positive Ventilation valve (PCV), Engine Control Module (ECM), Throttle Position Sensor (TPS), Coolant Temperature Sensor (CTS), Mass Airflow Sensor (MAF)... Timing may still be incorrect, worn camshaft/crankshaft, Lifters...

Do you have any Diagnostic Trouble Codes (DTC)?

ace322

Yes how could I forget to put what kinda car it is. It's a 91 z28 5.0 TPI. The spark advance is back under control and is idling fine. The only issue I have is the slight bog during acceleration and then when under light throttle on the road going about 40mph it surges a bit. I have an autoxray diagnostic tool and it's telling me my EGR duty cycle is at 99.4% the second I give it gas. No matter what temperature it's at it always tells me that percentage. I'm starting to think my egr valve is staying stuck open when giving it gas and that could be what's making it bog and surge.

John62591

My roommate removed his EGR system and put a chip in the ECM to never had a problem, but here's a site that goes into detail for the EGR system in paragraph 2, even though you don't have the code, it has accurate information.

ace322

Thanks appreciate it. I don't see the link to the website though

John62591

Haha **** here it is.. http://sethirdgen.org/egr.htm

ace322

Excellent info. I'm definitely thinking it's the EGR now because my EGR duty cycle goes straight from 0 to 99.4% no matter what speed I'm at so that tells me that it's not adjusting properly and that's why i feel that surge. Thanks you've been a great help

John62591

Your welcome! Get back to us for an update when you get a chance.

ace322

Ok so update on the issue with my camaro. Changed out the EGR and big difference! absolutely no bogging or surging anymore. Car is idleing great now and makes me love my car that much more again. Thanks for all the help John I really appreciate it

John62591

That's awesome I'm really glad you were able to check the EGR duty cycle. You were on the right track, props to you man. Thank goodness for thirdgen.

jayjay007

So was it the erg valve ? Or a different component of the erg? I'm having the same problem in my 1992 camaro rs

jayjay007

So was it the erg valve ? Or a different component of the erg? I'm having the same problem in my 1992 camaro rs

ASE doc

On that early system, duty cycle goes from 99.4 whenever EGR is allowed by the PCM. The EGR is not directly controlled by the PCM but by ported vacuum. The PCM, by way of the solenoid, only activates tor deactivates the ported vacuum supply to allow or disallow EGR operation. EGR is disallowed below 120f coolant temp or above 75% throttle.

When EGR is allowed, ported vacuum means that there is no vacuum to the EGR at closed throttle. Under load, there is reduced vacuum according to engine load. The EGR is only intended to be fully open at cruise, when ported vacuum would be about equal to manifold vacuum.

Since the new valve improved things, it's likely that the valve's return spring was broken or weak. The valve may also have been sticking.