low end surge when cold
Thread Starter
Intermediate
Joined: Jun 2012
Posts: 35
Likes: 2
From: kennesaw ga
low end surge when cold
87 110k stock
So latley I have an issue with a low end surge and stumble especially when cold... warmed up a little better.. Top end power for accel on highway fine.. Sensor?? vacum leak....????
I did a search but nothing popped??
Thanks
So latley I have an issue with a low end surge and stumble especially when cold... warmed up a little better.. Top end power for accel on highway fine.. Sensor?? vacum leak....????
I did a search but nothing popped??
Thanks
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
my 87 does something like this also...
rough idle when cold for a few seconds, smooths out, drives fine then suddenly there is a surge of fresh power/smoothness, crispness...that appears and makes it feel like it was running on 5 cyl and now all 8 are working. never quite figered it out. My best guess is injectors. Mine are less than 2 yrs old, but none the less, its NOT compression, its NOT spark related (as far as I can prove) so fuel is the onl;y thing left. Its either the inj OR possibly the cold start valve closing and the engine suddenly getting the right air/fuel ratio and surging as a reaction to that.
rough idle when cold for a few seconds, smooths out, drives fine then suddenly there is a surge of fresh power/smoothness, crispness...that appears and makes it feel like it was running on 5 cyl and now all 8 are working. never quite figered it out. My best guess is injectors. Mine are less than 2 yrs old, but none the less, its NOT compression, its NOT spark related (as far as I can prove) so fuel is the onl;y thing left. Its either the inj OR possibly the cold start valve closing and the engine suddenly getting the right air/fuel ratio and surging as a reaction to that.
Thread Starter
Intermediate
Joined: Jun 2012
Posts: 35
Likes: 2
From: kennesaw ga
starting is fine, idle is good.. low end power weak with stumble ,, feels like computer?? or something related,,, then breaks loose with full power.. better when warm but not gone.
Last edited by d914; Nov 26, 2012 at 10:18 AM. Reason: spelling
Race Director
Joined: Nov 2003
Posts: 12,221
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From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Injectors isn't a bad thought. Especially since L98 O2 sensors only monitor the DS cylinder banks. So, sticky injectors on the PS would go "unnoticed" by the ECM.
Another option is electronics/wiring. A faulty or intermittent connection anywhere in the MAF circuit might cause this issue. If the engine doesn't "see" any air for a millisecond, you could get stumbling. Of course, the problem could be in the distributor/injector-driver circuit too.
I found cure to my stumbling issue by cleaning the MAF plug and the ECM plug(s). It's been problem free for over 2 years.
There are several pathways that could cause similar malfunction though.
Note: To be clear, I eventually started to see MAF voltage low codes that led me to my diagnosis.
Another option is electronics/wiring. A faulty or intermittent connection anywhere in the MAF circuit might cause this issue. If the engine doesn't "see" any air for a millisecond, you could get stumbling. Of course, the problem could be in the distributor/injector-driver circuit too.
I found cure to my stumbling issue by cleaning the MAF plug and the ECM plug(s). It's been problem free for over 2 years.
There are several pathways that could cause similar malfunction though.
Note: To be clear, I eventually started to see MAF voltage low codes that led me to my diagnosis.
Last edited by GREGGPENN; Nov 26, 2012 at 12:51 PM.
Drifting
Joined: May 2005
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From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
I would start with making sure your Throttle Body and Idle Air Control motor is spotless.
Sometimes these items are forgotten and they need to be attended to on a regular basis.
Air is being pulled constantly into our engines and these parts see all the dirt that gets by the air filter. Believe me, that can be quite a lot of dirt!
Sometimes these items are forgotten and they need to be attended to on a regular basis.
Air is being pulled constantly into our engines and these parts see all the dirt that gets by the air filter. Believe me, that can be quite a lot of dirt!
