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+--- Thread: Revvn low poor acceleration (/showthread.php?tid=9515)
Revvn low poor acceleration - MRicci - 07-13-2011
So the car i bought from Jake has yet to let me down, but its still not running the way I want it to.
Not sure how many people here got to experience it themselves, but there is something that is preventing the car from accelerating to its fullest potential.
Ill try to explain as best I can.
When the car is cold, it starts up and occasionally and it will give a bit of hesitation driving off for the first and second time. When you get past that, and give it a little gas, it accelerates exactly like it should. As soon as the car warms up, the acceleration becomes lacking. The car cruises wonderfully, 80 mph no problem, but as soon as you need to take off from a light, you need to put your foot down to get it to accelerate half decently.
If you haven't seen the project thread, I've replaced the distributor cap and rotor, the plugs, refurbished the injectors completely and verified their function.
I have also tested the coil and wires for resistance and they were all in spec.
When the engine idles, it seems almost perfect but the motor shakes a little bit, like its misfiring. A mechanic told me that he was sure it's misfiring and he told me one of the exhaust valves isn't closing. I ran a compression test and all 6 cylinders showed 180 psi. No leaks at all.
I've been suspicious of the exhaust lately as it has been making a rattling noise upon acceleration. I currently have it disconnected at the manifold because the gaskets are rusted away. As soon as i remove the cat completely, I want to inspect it and make sure its not clogged.
I ran the car with no exhaust and it seemed to run similar to what it was with an exhaust. The engine was not perfectly smooth like it should be, and there was also the same type of hesitation while starting off. (it was super loud and awesome though)
Of course I didn't want to take the open headed e30 out for a spin on the main roads as the police would be on my case within a mile. Its back in the garage right now and I'm trying to find out as much as I can on the internet.
I also cranked the starter with the plugs out to check for spark strength and they emitted an orange spark. This could also be a problem but it doesn't make sense that the car sometimes accelerates extremely well, then just quits after 5 minutes.
Perhaps a fault in the computer?
I hope you guys have some good advice for me, the last thing I want to do is take it into a shop.
I suppose a few things I haven't tested should be considered as culprits. The fuel pressure regulator (unlikely), The motronic computer,
Re: Revvn low poor acceleration - Jake - 07-13-2011
Try swapping the Motronics ECU. The one installed now is (supposedly) chipped. Maybe something is going bust. There was a spare/original Motronics box in the trunk somewhere when I sold it to you. If that one works, you can run it on 87 gas, too.
Re: Revvn low poor acceleration - MRicci - 07-13-2011
heh, that was the first thing i did, ran the same. I suppose that may rule out the electronics problem
Re: Revvn low poor acceleration - BLINGMW - 07-14-2011
fuel pump, fuel filter?
Re: Revvn low poor acceleration - ViPER1313 - 07-14-2011
Have you verified the ignition timing? How does the distributor advance timing (electronically or by vacuum?) My thinking... as a car warms up, usually the distributor / engine computer should advance timing to compensate for the warm engine. If your base timing is off or the car is not advancing timing (because the distributor's base timing is set incorrectly, a vacuum switch is not functioning correctly, the engine computer is not telling the distributor to advance timing) you will have symptoms exactly like you describe (running well when cold but not warm, hesitation, running rough at idle, etc...)
Re: Revvn low poor acceleration - Kaan - 07-14-2011
when the exhaust was off did you check the cat? usually when its clogged you wont be hitting 80mph though. all the other symptoms are the same though.
Re: Revvn low poor acceleration - NTIman - 07-14-2011
Did you check the coil and the wires while they were hot? Many times the ignition won't break down until the system is up to temperature. I've seen several cars like that, including my old escort.
Secondly, what brand of plugs did you install?
Re: Revvn low poor acceleration - NTIman - 07-14-2011
EGR system issue? Throttle position sensor issue?
Re: Revvn low poor acceleration - Jake - 07-14-2011
BLINGMW Wrote:fuel pump, fuel filter?
Filter was replaced under my ownership.
Re: Revvn low poor acceleration - MRicci - 07-26-2011
The PPO said the timing belt was done, but I have no way to verify it. I bought brand new ngk sparks along with a new distributor cap and rotor. The wires haven't been replaced yet, and they showed resistances of about 2500 ohms. I have not checked the ignition while it is hot. What would I be looking for? bad resistances?
The one thing that confuses me is the good ignition on 5 of the 6 cylinders (indicated by the spark plugs) and the single poor cylinder (black sooty material on the spark ceramic) I think thats what warranted the misfire verdict from the mechanic.