has anyone had this problem
 

i have a 1988 chevy cheyenne with a 305 tbi engine. about a year ago i replaced the injectors from jon at fic injectors. i also replaced the fuel reg the egr the idle air control valve the map plugs wires cap rotor and fuel pump. it has always had a miss even after all that. what it does is if i'm backing out of my driveway and stop to put it in drive it will start to stall like it want too shut down. i stop at a light and it does the same thing. now it doesn't do it all the time but it does it most of the time. if i'm on the highway and i let off the gas it will stall and sometimes it will shut down. i have been trying to fix this for over a year and have not been able to figure it out. i thought it might be the brake booster but it does it when i let off the gas with out stepping on the brake. it has no vacuum leaks. can anybody help

Re: has anyone had this problem
 

What is it idling at?

If you raise the idle with the throttle just a little to say 900 at idle, do you feel a miss?

Have you tried to identify a dead cylinder?

Re: has anyone had this problem
 

yes you can still feel a miss when you raise the idle and no dead cyclinders other then what it does when you let off the gas the truck runs great you can step on it and it will not stall it will burn the heck off the tires if you step on it too hard the motor has lots of power for 177000 miles my dad owned it before me and he did take good care of it

Re: has anyone had this problem
 

You'll have to convince me you don't have a dead cylinder. If you have a miss at an elevated idle it just has to have one.

Do you have headers and an IR thermometer?

Re: has anyone had this problem
 

Pull the vacumn line off the egr valve and plug it and go for a drive. Even though you replaced it it can still be a problem. House brand valve or
Delco?

Re: has anyone had this problem
 

Double check plugs & wires. Not unusual to assume new ones are alright, when one is defective or damaged. ( look closely at plugs) ( ceramics for a hair line crack)...

Continuity of wires.

I have MSD wires and 2 had a loose fit at the plug end. I moved it and the continuity fluctuated .....so it didn't 'miss' all the time. It took a while to figure that out.

Re: has anyone had this problem
 

speedy it does not have a miss all the time it will only miss when i let go the gas when I'm driving but it will go back to its regular idle when it is stopped it idles fine i turn it on and it idles normal i put it in drive and it idles normal i start to drive and leave go the gas and it wants to shut down but goes back to its normal idle sometimes it shuts down but it will start up and idle normal do you get what i mean i don't have to keep my foot on the gas to keep it running it runs normal. it has no headers its all factory. yes i have an Ir thermometer what would you like me to check. Mountie i checked the egr it is working fine so are the plugs and wires all parts are delco it was doing this before i replaced the parts and still is. i do have everything to rebuild the motor and was going to do it 3 weeks ago but someone T boned the car my wife drives so i had to let her use my other truck and put this one back on the road

Off idle is is usually the EGR.
 

Now what you clearly explained is a definite EGR problem. So just to squelch me and the other guy. Pull and plug the vac line and take it for a spin. If it still does it, I won't suggest it again.

As far as the IR therm goes, If you had headers, I was gona have you look for a cooler then the rest pipe. Can't do it with stock manifolds.

What do you mean by "rebuild". If you think a mechanical rebuild of the lower half will have a chance of fixing the problem, then that can be tested for in several ways. The least of which is compression and a leak down test. But I'm sure I must be mistaken regarding what you meant by "rebuild".

Re: has anyone had this problem
 

Only 4 months ago I had the most frustrating "on -n-off" / "runs-then-doesn't run -good" problem. My Engine Control Module. It sometimes felt like vacuum, sometimes it felt like Fuel, sometimes it felt like Ignition.

Re: has anyone had this problem
 

i replaced the egr since i had a new one that i was going to replace when i rebuild the motor and it is still doing the same thing as for the rebuild i have everything to rebuilt the engine new crank all the bearings piston rings cam lifters oil pump valves and springs rockers push rods water pump all seals and gaskets distributor and all the sensors i work at an auto parts store so it didn't hurt my wallet to much but i had to put it on hold till i can get another car for my wife mean while i have to figure out what is wrong with this truck

Re: has anyone had this problem
 

Somebody near you must have a Snap-On diagnosis tool.

Computer chip...... ECM....... Dist........Coil.......TPS.......Wires....Plugs......Harness.......short in IGN @ key lock........vacuum........ valve train........ martini...... scotch......Tequila...that funny smelling cigarette...... a real Cuban Cigar...

Re: has anyone had this problem
 

check for a tight distributor shaft..these TBI distributor's are known for getting lack of oil in them. and will make it stall and idle funny..

pull out the dist. look at the magnet on the pickup coil..If there are cracks in the magnet..that will cause a miss..and check the shaft..

the magnet in the pickup coil controls the injector fire rpm too.

Get a good reman one..or a good used one..but spin it 1st..I worked on 91-93 caprice taxi cabs and they all did the same thing..very common , we used them from napa..and they worked...used them from advance and they did not. napa had a better quality part...a few more bucks but worht it.

I had had over 50+ of these trucks do the same thing..

Re: has anyone had this problem
 

Does it ever set a code?

Re: has anyone had this problem
 

Only if it causes another serious symptom to set it off.

I could not remember how to describe that part of the distributor, but I am in agreement with 70blazerx2.

Even though I replaced both my ICM and Coil ( they both went bad during the same time) That was a tough nut to crack!

I am wondering if my magnets/springs are weak. The way to do a simple test is a timing light....... (disconnect wire for timing light).... at idle see timing mark......raise idle and see if timing mark fluctuates... Could very well be that.
( something like that....)

A real tuner would give a better description how to perform the check.

(edit)..... Huh...... just noticed...... My 100th post.......:metal:

Re: has anyone had this problem
 

OK guys i think i found the problem i removed the egr vacuum solenoid and put a straight line to the egr and it stopped missing i am going to replace the egr vacuum solenoid to see what it does and ill let you all know what happens thank you guys

Re: has anyone had this problem
 

Hope it works!! I forget your year/ model truck..... Sometimes during the previous posts, the year truck is forgotten. Sometimes a response may not work for your year.

I suggest to include the year truck in the post title?

Re: has anyone had this problem
 

Update????

Re: has anyone had this problem
 

There's a lot of stuff to check.... it will be a process....

Was interested in what happened related to the EGR fix....
 

I appreciate you telling us it would take a long time to check things. :rolleyes:

However, I was only interested in what HE described was the fix that he already figured out. It has been 10 days to change what he described as only changing a solenoid.