88 Chevy Tbi 350 misfiring
December 29th, 2015, 12:01 AM
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88 Chevy Tbi 350 misfiring
Hello guys! New guy here....
I recently got me a 88 chevy 1500 with a 350 tbi - I had a few issues with it but nothing that was more annoying then running issues..... Need some help....
Two weaks ago I went to pick up a 88 long bed chevy pick up - Uppon getting there this was one of the ugliest trucks iv ever seen but a test drive changed my mind completely about this truck.....
It ran and drove like new.
Did not smoke what so ever.
Cold started awsome.
Shifted and pulled really hard.
Wot at 35 to 40mph broke lose the tires.
I mean this thing drive perfect (Great ride quality - no shaking - pulling or rattling - slam on the brakes and comes to a perfect stop with out darting - no issues......
As soon as i paid then man I pulled away and the thing developed a hard miss.... It acted as if a cylinder was down. (Figures)....... I thought maybe i had picked up trash in the tank because it was low on fuel.....
Added fuel but the misfire was still there even after 30 miles+........
The next day I was checking thing under the hood and cleaning things a lil (And i cant tell you what i did) but the next time i started it the misfire was gone... So a few days later I went ahead and changed the plug wires (Found one burned)...... Anyhow this was the last of the misfire issue.....
It was back to being like new....
However one issue i have had with this truck is it seems to have a hard time figuring out its idle....
Sometimes it would wanna idle 1100ish rpms - and others it would idle fine (Didnt matter if it was hot or cold)
Sometimes you would start it and it would be around 800ish maybe less and others way high.... In gear it dident seem to be as noticeable but i could slightly tell differences.... It may idle high and then shut it off and turn it right back on and idle fine.....
So I kinda did some digging - I cleaned - The AIC - The Throttle body (has no play to it* Wiggling it does not effect it) - I installed a new TBI gasket - I checked vacuum lines - The temp sensor seem good cause the temp gauge works)- checked and cleaned egr but nothing seemed to fix it..... I just learned to live with it
Has done fine since....
a few days ago went to okc 200 miles - it drove fine there and back...
After being home a day - I took it out and drove it a bit - did fine..........
Went and got fuel.... 3 miles later - I noticed a shutter or stumble on take off.... and since that moment it has got worse....
Here is what it does now.....
Idle is fine - in gear or in park..... Reving or taking off causes the issue....
It stumbles - It almost acts as if the tps is failing or it leaning out....
You can take off and it will stumble/misfire but play with the pedal (Mainly easy up on it) and it clears up.... It will sometimes flat out fall on its face and easing up will get it going again....
Sometimes you can wot it and it cleans up - other times it just acts as if the power is going away like lack of fuel.
Earlier when i was checking it out a few times it popped (FIRE BAD
) threw the tbi. No big ball of flame but a small ball of light.....
Its not a hard miss like when i got it - Its like a breaking up falling on its face misfire.....
One thing I noticed was - Shutting it down and cycling the key a few times and then starting it will cause it to disappear for a few secs (fuel pump?)
At one point i was driving down the highway and I shut it down while coasting and cycled it a few times and when i restarted it acted ok for a few secs under load.......
I know it has a roller cam - and roller rockers.
The trans is new.
Will literally destroy the tires on take off.
35 and 40 it will brake the tires lose...
Barks tires when it shifts...
Has new tires and underside parts all the way around.
No rust...
The paint is just Dogged - its gone....
Anyone got any clue wear i should start checking?
Thanks for everyones time!
I recently got me a 88 chevy 1500 with a 350 tbi - I had a few issues with it but nothing that was more annoying then running issues..... Need some help....
Two weaks ago I went to pick up a 88 long bed chevy pick up - Uppon getting there this was one of the ugliest trucks iv ever seen but a test drive changed my mind completely about this truck.....
It ran and drove like new.
Did not smoke what so ever.
Cold started awsome.
Shifted and pulled really hard.
Wot at 35 to 40mph broke lose the tires.
I mean this thing drive perfect (Great ride quality - no shaking - pulling or rattling - slam on the brakes and comes to a perfect stop with out darting - no issues......
As soon as i paid then man I pulled away and the thing developed a hard miss.... It acted as if a cylinder was down. (Figures)....... I thought maybe i had picked up trash in the tank because it was low on fuel.....
Added fuel but the misfire was still there even after 30 miles+........
The next day I was checking thing under the hood and cleaning things a lil (And i cant tell you what i did) but the next time i started it the misfire was gone... So a few days later I went ahead and changed the plug wires (Found one burned)...... Anyhow this was the last of the misfire issue.....
It was back to being like new....
However one issue i have had with this truck is it seems to have a hard time figuring out its idle....
Sometimes it would wanna idle 1100ish rpms - and others it would idle fine (Didnt matter if it was hot or cold)
Sometimes you would start it and it would be around 800ish maybe less and others way high.... In gear it dident seem to be as noticeable but i could slightly tell differences.... It may idle high and then shut it off and turn it right back on and idle fine.....
So I kinda did some digging - I cleaned - The AIC - The Throttle body (has no play to it* Wiggling it does not effect it) - I installed a new TBI gasket - I checked vacuum lines - The temp sensor seem good cause the temp gauge works)- checked and cleaned egr but nothing seemed to fix it..... I just learned to live with it
Has done fine since....
a few days ago went to okc 200 miles - it drove fine there and back...
After being home a day - I took it out and drove it a bit - did fine..........
Went and got fuel.... 3 miles later - I noticed a shutter or stumble on take off.... and since that moment it has got worse....
Here is what it does now.....
Idle is fine - in gear or in park..... Reving or taking off causes the issue....
It stumbles - It almost acts as if the tps is failing or it leaning out....
You can take off and it will stumble/misfire but play with the pedal (Mainly easy up on it) and it clears up.... It will sometimes flat out fall on its face and easing up will get it going again....
Sometimes you can wot it and it cleans up - other times it just acts as if the power is going away like lack of fuel.
Earlier when i was checking it out a few times it popped (FIRE BAD
) threw the tbi. No big ball of flame but a small ball of light.....Its not a hard miss like when i got it - Its like a breaking up falling on its face misfire.....
One thing I noticed was - Shutting it down and cycling the key a few times and then starting it will cause it to disappear for a few secs (fuel pump?)
At one point i was driving down the highway and I shut it down while coasting and cycled it a few times and when i restarted it acted ok for a few secs under load.......
I know it has a roller cam - and roller rockers.
The trans is new.
Will literally destroy the tires on take off.
35 and 40 it will brake the tires lose...
Barks tires when it shifts...
Has new tires and underside parts all the way around.
No rust...
The paint is just Dogged - its gone....
Anyone got any clue wear i should start checking?
Thanks for everyones time!
January 5th, 2016, 10:25 PM
#3
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I just rebuilt a 89 350 tbi. I seem to remember there being a sort of filter/screen inside the tbi itself. Could have junk in it. Also chech that lil 2 wire sensor by the thermos housing. I accidentally cracked mine and upon startup it was all over the board rpm wise, guessing cause it was bounce contacting. New one fixed that. The way you describe the way you take your foot off the gas clears it up reminds me of a tps I had that went bad. New tps and prob solved and ran better. I think your on the right track. I would also check your fuel lines, make sure vent is working. The stupid lil things can be a pain.