Here we go again....
02-15-2011, 08:49 PM
#1
Here we go again....
My 86 is still giving me problems. I just changed the injectors on it and the idle quality and throttle response improved significantly, but it still has a hiccup on acceleration. The car still isn't giving any codes. Could someone please help me with this? I'm all out of ideas...
And fuel pressure and timing and poor plug wire, yada yada 
02-15-2011, 11:16 PM
#4
I've checked all the basic stuff, new plugs, wires, etc. etc... I didn't think it would be the timing cause it would do that throughout the whole rpm range? it seems like it only does it above 1800 when accelerating or going up a hill. Could it be a worn timing chain? I also tried cursing at it, but that didn't help...
02-15-2011, 11:49 PM
#5
Racer
Need a little more info... define "hiccup on acceleration" - just one hiccup and then normal or does it continuously misfire above 1800 RPM - also does it only do it under light throttle and clear up at heavy throttle application, etc. Does it clear up at the upper RPM's or not, ETC.
Gotta narrow it down to a continuous misfire, a quick stumble at throttle tip-in, stumble at only certain throttle positions, etc.
What parts exactly have you replaced (cap, rotor in addition to the plugs/wires?)...
I'd say if you've replaced all the standard ignition stuff and checked the coil resistance when swapping it to the new cap then get a DVM to start checking the sensors (TPS, IAT, CTS, etc.) for proper range and operation. (a service manual helps here or do some searching for test methods)
Gotta narrow it down to a continuous misfire, a quick stumble at throttle tip-in, stumble at only certain throttle positions, etc.
What parts exactly have you replaced (cap, rotor in addition to the plugs/wires?)...
I'd say if you've replaced all the standard ignition stuff and checked the coil resistance when swapping it to the new cap then get a DVM to start checking the sensors (TPS, IAT, CTS, etc.) for proper range and operation. (a service manual helps here or do some searching for test methods)
02-16-2011, 02:01 AM
#6
Safety Car
Check the wires that connect to the moduel in the distributor.The plastic gets hard and cracks and causes the engine to cut out and stumble at times.Check everything in the distributor.
02-16-2011, 12:53 PM
#7
bwiencek, it is like a miss and it does not seem as bad at higher revs and at more throttle. Red, You think the connectors could be arcing over to each other? Do you guys think this could be a timing problem?
02-21-2011, 01:28 PM
#9
Race Director
Did you ever check the tps sensor as suggested earlier?
02-22-2011, 08:21 AM
#12
Racer
That's actually good news that you can hear it at idle (makes troubleshooting a little easier)
Do you have a timing light?
If so then one at a time hook it up to the plug wires and watch the pattern of the light flash - when it misses check and see if the light "skips a beat" - which I'm betting it does - and that means you've got an ignition problem somewhere.
I know you said that you replaced the cap & Rotoro, but if you got the cheapest parts store chineese import cap/rotor then take it back and have them replaced - I've had some that were so bad the vehicle was really hard to start then after a couple days it wouldn't even start - drove me nuts until I put the old stuff on and it ran like a top - got a bosch replacement and it ran fine until I sold it...
Next thing I would check is the wires in the distributor base - pull the distributor cap and look real close at the wires that go from the body to the computer and then from the body to the cap terminals - the plastic has a tendancy to 'dry out' and almost disintegrate - the wires can chaff through the insulation and cause timing and spark issues.
If the timing light doesn't show an ignition skip then I'd start looking at compression testing the engine (or leakdown test), and when you're doing that check the condition of the plugs for over fueling (rich) or signs of lean detonation.
Do you have a timing light?
If so then one at a time hook it up to the plug wires and watch the pattern of the light flash - when it misses check and see if the light "skips a beat" - which I'm betting it does - and that means you've got an ignition problem somewhere.
I know you said that you replaced the cap & Rotoro, but if you got the cheapest parts store chineese import cap/rotor then take it back and have them replaced - I've had some that were so bad the vehicle was really hard to start then after a couple days it wouldn't even start - drove me nuts until I put the old stuff on and it ran like a top - got a bosch replacement and it ran fine until I sold it...
Next thing I would check is the wires in the distributor base - pull the distributor cap and look real close at the wires that go from the body to the computer and then from the body to the cap terminals - the plastic has a tendancy to 'dry out' and almost disintegrate - the wires can chaff through the insulation and cause timing and spark issues.
If the timing light doesn't show an ignition skip then I'd start looking at compression testing the engine (or leakdown test), and when you're doing that check the condition of the plugs for over fueling (rich) or signs of lean detonation.
02-22-2011, 09:23 AM
#13
Le Mans Master
........... Do a night time arc check under the hood ... also , make sure the plug wires are sufficiently separated ... half inch minimum ... parallel wires can induce voltage in their neighbors ... particularly #5 and #7 ... #8 and #4 ... and we wont even ask if you have verified the firing order vs plug wires at the distributor - 18436572 - and at the plugs ..........
02-22-2011, 10:22 AM
#14
- 1986 Original Owner -
Sounds a bit like Pick-up Coil to me.
02-22-2011, 12:15 PM
#15
Racer
Agreed with most of those above, weak spark will cause a part throttle stumble that is much less noticeable at full or idle (part throttle is both lean and includes EGR gas).
Bad plugs, wires, cap rotor. Weak ignition coil, improper plug gap etc. I've had 2 injected GM cars, both would stumble and buck at about enough throttle to pass on the highway without causing the tranny to kick down. Both cars it was a sign for me to give them new wires and plugs and every time that cured it. Put a meter on each ignition wire and make sure the resistance isn't too high.
Bad plugs, wires, cap rotor. Weak ignition coil, improper plug gap etc. I've had 2 injected GM cars, both would stumble and buck at about enough throttle to pass on the highway without causing the tranny to kick down. Both cars it was a sign for me to give them new wires and plugs and every time that cured it. Put a meter on each ignition wire and make sure the resistance isn't too high.
02-22-2011, 01:13 PM
#16
Thanks for all the great info guys. When I replaced the ignition module, I noticed the plastic connector for the 5 pin side was broken, do you think it they could be arcing there? bwiencek, I don't think I understood that very well, do you men the wires that go into the base of the dist and to the icm?
02-22-2011, 07:32 PM
#17
Melting Slicks
doubtfull if it is the wires in the dist arching. If you can here and feel the miss at idle pull wires from injectors one at a time. Do this untill it does not change the way the car idles. If done right and infact you do have a cyl. missing this is a sure fire way of locating it.
02-24-2011, 04:18 PM
#18
Racer
First part was about checking cap to plug wires with the timing light, second part I was referring to the wires in the base of the distributor - which you already know the plastic around the wires is all broken up so I'd be checking those wires over real well and either replacing the plastic wire holder or at least wrapping them in tape to prevent them from rubbing against the distributor body.
My guess is that a timing light hooked to each plug wire one at a time will locate the miss...
My guess is that a timing light hooked to each plug wire one at a time will locate the miss...
02-24-2011, 06:17 PM
#19
Melting Slicks
No being a smart @ss but the timeing light on each plug wire is hit or miss. With that you are assuming that it is a ign problem. If you pull the injector wires you are totaly elimating that cyl. If you get no difference you are more or less down to checking compression. fire and fuel for that cyl.
03-02-2011, 12:58 PM
#20
I found a vacuum leak, plugged that, readjusted the TPS, but still having the problems. Now it's only at higher RPM or when going up a hill. Since this happens when the ECM is in open loop and closed loop could it be an issue with the ECM?