Rough Running in Low RPMs
Thread Starter
Racer
Joined: Jul 2001
Posts: 253
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Rough Running in Low RPMs
As my sig shows, it's an '86 4+3. Not sure what's going on. I get a 'Service Engine Soon' once every few weeks and it's showing a code 43 (knock sensor).
Symptoms are a little rougher idle than normal and chugging at low RPMs. It starts to clear up around 1700 RPM. It starts fine. These symptoms started yesterday, all of a sudden.
Old school tells me this is an EGR problem. I did a search in the posts/archives and see that I shoud be getting a code 32 if the EGR is acting up and that there's a solenoid behind the air pump? I didn't see that.
I tried to test the EGR by reaching my fingers under the runners to push on its diaphram to see if the idle would stumble, but I can't get my fingers in there to push on it.
Any thoughts?
TIA
Symptoms are a little rougher idle than normal and chugging at low RPMs. It starts to clear up around 1700 RPM. It starts fine. These symptoms started yesterday, all of a sudden.
Old school tells me this is an EGR problem. I did a search in the posts/archives and see that I shoud be getting a code 32 if the EGR is acting up and that there's a solenoid behind the air pump? I didn't see that.
I tried to test the EGR by reaching my fingers under the runners to push on its diaphram to see if the idle would stumble, but I can't get my fingers in there to push on it.
Any thoughts?
TIA
Thread Starter
Racer
Joined: Jul 2001
Posts: 253
Likes: 0
Re: Rough Running in Low RPMs (vader86)
There was a loose connection in the knock sensor wiring harness. So, I'm back to ask about the low rpm stumbling. Idle is rough. Low rpm stumbling. Drive at low rpm and then give it some gas and it starts bucking. No codes. 2nd tank of gas, hopefully eliminating the fuel as an issue.
I was thinking the EGR had something to do with it, but I can feel the 'missing' at mid-range to higher rpms, although it's more difficult to feel, where the EGR is best felt at low rpms. I could get a vacuum tool, like a Mighty Vac to see if the EGR holds vacuum...
I've got a 'spark-checker' that for lack of a better term, that looks like a pen. When held against the spark plug boot a 'spark-like flash' is seen in a clear part of the 'spark-checker'. I've got new spark plug wires - OEM. I cleaned the cap (pick and ignition file) about 1000 miles ago.
I've read a little about the Mass Air Flow and Idle Air Control, but I didn't see anything that was specific enough to my problem.
Anyone got any ideas?
Thanks
I was thinking the EGR had something to do with it, but I can feel the 'missing' at mid-range to higher rpms, although it's more difficult to feel, where the EGR is best felt at low rpms. I could get a vacuum tool, like a Mighty Vac to see if the EGR holds vacuum...
I've got a 'spark-checker' that for lack of a better term, that looks like a pen. When held against the spark plug boot a 'spark-like flash' is seen in a clear part of the 'spark-checker'. I've got new spark plug wires - OEM. I cleaned the cap (pick and ignition file) about 1000 miles ago.
I've read a little about the Mass Air Flow and Idle Air Control, but I didn't see anything that was specific enough to my problem.
Anyone got any ideas?
Thanks
Race Director
Joined: Aug 2000
Posts: 14,130
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Cruise-In II Veteran
Re: Rough Running in Low RPMs (86VetteBill)
If the esc 43 is fixed now and isnt the problem,
Could be a few things...first check the fuel pressure.
It would also help to have a scanner to see what the maf,tps and etc is reporting.
Without a scanner,sometimes its an expensive guess by throwing parts at the car.
Hows the cap/rotor/module and coil btw?
What about IAC and other TPI parts..they new or really old?
Could be a few things...first check the fuel pressure.
It would also help to have a scanner to see what the maf,tps and etc is reporting.
Without a scanner,sometimes its an expensive guess by throwing parts at the car.
Hows the cap/rotor/module and coil btw?
What about IAC and other TPI parts..they new or really old?
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: Rough Running in Low RPMs (86VetteBill)
If just rough idle and not low rpm misses, clean the TB and blades.
Verify base idle is 450rpm (with IAC pintel fully extended) and TPS voltage at base idle is between 0.54Vdc and 0.65Vdc.
Verify base timing is at +6deg and use the timing light on each wire to assure that there is no misfire on any plug.
If the EGR is faulty the ECM will throw the code. The solenoid may be on top of the base manifold, as is mine.
Verify base idle is 450rpm (with IAC pintel fully extended) and TPS voltage at base idle is between 0.54Vdc and 0.65Vdc.
Verify base timing is at +6deg and use the timing light on each wire to assure that there is no misfire on any plug.
If the EGR is faulty the ECM will throw the code. The solenoid may be on top of the base manifold, as is mine.
Thread Starter
Racer
Joined: Jul 2001
Posts: 253
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Re: Rough Running in Low RPMs (65Z01)
Up front, let me say that I've just order the shop manual from Helm's. :yesnod:
I can describe this as a rough idle that feels like a miss above idle. Under load at low rpms (just above idle to about 1200) I can just "see" the motor shaking right out of its mounts.
"If just rough idle and not low rpm misses, clean the TB and blades."
A little direction is appreciated here with the 'TB and blades'. While I'm waiting for my Helm's delivery (3-4 days), is the library version of Chilton's going to show me where these parts are? :confused:
"Verify base idle is 450rpm (with IAC pintel fully extended) and TPS voltage at base idle is between 0.54Vdc and 0.65Vdc."
I've pulled some information about this procedure from Cajun that will help me with this & MAF, . Still don't know where they're at.
:
"Verify base timing is at +6deg and use the timing light on each wire to assure that there is no misfire on any plug."
I have a tool called the CT436 Firing Indicator by Champion. It's shaped like a pen and you hold it up to the spark plug boot to and see a flash inside its 1 inch tube in the middle of the tool. All plugs are firing steadily, but I want to replace them anyway. I'll check the timing, too.
I can describe this as a rough idle that feels like a miss above idle. Under load at low rpms (just above idle to about 1200) I can just "see" the motor shaking right out of its mounts.
"If just rough idle and not low rpm misses, clean the TB and blades."
A little direction is appreciated here with the 'TB and blades'. While I'm waiting for my Helm's delivery (3-4 days), is the library version of Chilton's going to show me where these parts are? :confused:
"Verify base idle is 450rpm (with IAC pintel fully extended) and TPS voltage at base idle is between 0.54Vdc and 0.65Vdc."
I've pulled some information about this procedure from Cajun that will help me with this & MAF, . Still don't know where they're at.
:"Verify base timing is at +6deg and use the timing light on each wire to assure that there is no misfire on any plug."
I have a tool called the CT436 Firing Indicator by Champion. It's shaped like a pen and you hold it up to the spark plug boot to and see a flash inside its 1 inch tube in the middle of the tool. All plugs are firing steadily, but I want to replace them anyway. I'll check the timing, too.
