corvetteharley

Hi all again I posted before about my 86 vert having hiccups well this weekend I'm buying plugs and wires it has a very faint miss sometimes but when you punch it alls ok. The thing is when car reaches normal warm temp of 168 while driving down road release gas peddle when car idles down and coasts at idle the car starts jerking forward and backwards you punch gas no stall or miss car runs fine you let idle down starts hiccuping again. I'd replaced tps before and set timing,idle and tps to specs. Would the iac cause this to happen it never did it before I'd replaced the tps I also installed a new harmonic balancer at the time and cap n rotorbutton. Plugs were clean burn so put back wires I'd replaced with some used from before. I checked fuel injectors as one of you suggested all good cylinder 8 injector was one ohm less than all others and the other seven were exactly the same hot and cold same on 8. As said replacing plugs n wires this weekend that'll fix miss but jerking has me baffled. Any help appreciated thanks all

corvetteharley

Ps. There's no codes

tehcarguy

So this only happens when you let off the throttle?

blackbear bob

Just a thought, 168 is too cold for that engine to run well, also check fuel pressure.

corvetteharley

Yeah only when you let off gas and car cruises at idle and when car is stopped right before you press on the gas as car accelerates it's ok but it doesn't do it when cold at all.

RetiredSFC 97

Rule out the IAC by cleaning it and then move on. I agree with a complete FP check/test.

When the car is cold the car runs faster so it could very well be a fuel delivery issue when it gets warm. FPR possibly.

Frizlefrak

Check your EGR valve.

RetiredSFC 97

I agree

corvetteharley

Right before all the snow I bought new plugs and wires. I don't have a garage or car port so had to wait. The Friday of the snow my wifes Kia broke it's timing belt I have two babies and two older boys so needed two fix hers. I've never done a timing belt so printed of net instructions, out in the snow I'm tearing the whole front end of het car apart finished the teardown next day it took me that long just yesterday about 3 hours reassembled only to find out valves bent and water gushing from under I was mad. So today I worked on mine. Took for drive it doesn't jerk anymore when idleing down road or when stopped I'm happy. I still want the fuel pressure checked don't have the tool have to find time when coworker can check. Thanks all for your help. Oh Blackbeard I've always used a 165 temp thermostat in the summer it usually runs hotter about 180 ish to 190 ish sitting still once driving it cool back down. I was told not to let it get above 220 to shut it down and let cool.

steverichmond

I hate working on them outside and I feel you pain. Most major Auto Parts chains have a tool loan program. Perhaps that would be on way to check you FP. Good Luck.


Steve