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1990 Pontiac transport stumbles on idle in drive


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dougnsheena
User

Dec 10, 2012, 7:59 PM

Post #1 of 7 (1317 views)
1990 Pontiac transport stumbles on idle in drive Sign In

I have a 3.1 v6 Pontiac transport. When coming home today, I went to stop at a light and the van tried to die for no reason. Did this all the way home when I had to stop at a light, but drives fine when accelerating. I looked at the two tbi injectors and noticed one spraying great and one struggling with a weak spray and drip. Can the injector be causing the issue. Idle is erratic when stopped, sometimes fine, then drop to almost dying, then can raise the rpms above normal all in one stop. No codes or check engine light


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 10, 2012, 8:05 PM

Post #2 of 7 (1308 views)
Re: 1990 Pontiac transport stumbles on idle in drive Sign In

Does it feel like it's trying to push you when coming to a stop?

Does it run good in Park?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



dougnsheena
User

Dec 10, 2012, 8:08 PM

Post #3 of 7 (1297 views)
Re: 1990 Pontiac transport stumbles on idle in drive Sign In

No it doesn't, it feels as if it should stop just fine, but then the engine will sometimes stumble due to really low rpms like it is going to die. Other times it will be normal for a few seconds to up to 30 seconds then will act up. If I two foot it, to keep the rpms up it wont try to die. It will do the same in park or neutral. But when driving it is fine.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Dec 10, 2012, 8:10 PM

Post #4 of 7 (1290 views)
Re: 1990 Pontiac transport stumbles on idle in drive Sign In

You may have a bad IAC ( idle air control) but try eliminating any vacuum leaks and cleaning the throttle body first. Remove the intake snorkel, have someone hold the throttle wide open for you and scrub the back side of the throttle plate and surrounding bore with an old tooth brush and some carb cleaner. Be sure to spray some into the small holes next to the throttle plate. That should help stabilize the idle. If it still has a problem, replace the IAC.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
Veteran / Moderator
Sidom profile image

Dec 10, 2012, 8:24 PM

Post #5 of 7 (1282 views)
Re: 1990 Pontiac transport stumbles on idle in drive Sign In

If you have an ohm meter, check the resistance on both injectors & post the readings...


dougnsheena
User

Dec 10, 2012, 8:30 PM

Post #6 of 7 (1273 views)
Re: 1990 Pontiac transport stumbles on idle in drive Sign In

I do not have an ohm meter, but I can see that one injector sprays great and the other one is weak. when the van almost dies the weak injector barely has any fuel coming out.


dougnsheena
User

Dec 11, 2012, 1:01 PM

Post #7 of 7 (1231 views)
Re: 1990 Pontiac transport stumbles on idle in drive Sign In

I cleaned out the Iac today, and was able to drive the van for about 8 miles on city streets, then out of the blue it does the same thing, low stumbling idle sometimes, but not always, low rpms, sometimes followed by a surge in rpms for a few seconds etc. I pulled the codes and got 33 and 34, but I dont see anywhere that a map sensor can cause the iradic idle, hesitation on acceleration etc. I thought that was only the Iac. By the way the computer did not show the check engine light, I just checked the codes for the heck of checking the codes.






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