todzilla

I am the very happy and proud owner of a bone stock '86 951 - I've had it for 3 weeks and so far, she's been flawless.......

On my way home tonight, I put my foot into it on the highway home and and normally, she pulls hard and consistently with no glitches - tonight, not so much!!

As soon as the revs climbed to about 4 grand ( I was into it and the turbo was about to kick in) - the car jerked and sputtered and seemed to backfire!? I thought maybe it wasn't fully warmed up as I'd only been about 10 minutes into my drive so thought not much of it. I drove normally and easily til about another 10 minutes and tried again - put the foot down and she did the same sputtering/backfire or misfire thing!! I have done nothing odd EXCEPT I put in some concentrated injector cleaner ( on an empty tank) and filled it all the way up (92 octane) shortly after doing so. There was no tinkering under the hood and up til tonight, was always strong and smooth when I wanted that spool to kick in.

What did I do or where should I look? I can't get the car into see SCAN in North Van for about a week so any advice is needed.

Thanx guys!

todzilla

^^ oh yeah - I didn't use my usual Chevron 92 but Esso......which - now that I think of it - was 91 octane!

mortymower

It could be a giant vacuum leak. I blew off my hose from the intercooler pipe to throttle body and it stayed attached barely so driving around was ok, but when I hit it hard the air just leaked out the sides and it sputtered like crazy. Check all big air lines, also it could be ignition related (plugs, wires, distributor cap/rotor). Let it idle at night and go look at the plug wires and see if they are arching to the engine. Lindseyracing.com has a complete tune up kit for this stuff for like 150.00. That happened to me as well once. good luck

lart951

Maybe you are overboosting? due to a bad cv valve or a boost line got disconnected.

Keithr726

So it only happened when you tried to accelerate? If so, I was having the same problem before I took my car apart. There are many things that could cause this. Check the throttle position switch on the throttle body. With the car off push the throttle cam, you should here a click when it opens and a click when it pulls itself closed.

awilson40

after its does this "sputtering/backfire or misfire thing" does it then only boost to 1.2 bar on the stock guage ??? If so , you are triggering the safety mode and can retrieve fault codes to point you in the right direction.
It could be any of the suggestions listed above, when mine did this is was a bad TPS, easy thing to replace and not too pricy.

todzilla

^ re triggering the problem at 1.2 bars......I'll check that out this afternoon. That would seem to be accurate but I'll confirm it when I go for a drive. I'll also check all vacuum lines and any exposed hoses to see if there are any loose fittings or leaks, and I'll also check the tps.

Much thanx for all the advice guys.

Oh, and I will be getting a full tune up done on Monday (plugs, cap, rotor, wires and fuel filter the following Monday)

lart951

Have your mechanic check your cycling valve

todzilla

Well, it seems as though it cuts off the fuel (or so it feels) as it kind of 'hits' a wall' and jerks and backfires as soon as it hits about 1.6 bar.......when you get into it - be it gradually or abruptly - as soon as the boost is building, it just sorta coughs and there seems to be like a rev limiter kinda feel to the car......doesn't matter what gear! It's not a good feeling.

I can't get it into my mechanic for a week and honestly, I don't feel overly confident tinkering with the car in depth until I get a decent shop manual. I looked into getting a full tune up locally and they want $100 for the rotor, $60 for the cap (all Bosch) - $12 for plugs (NGK) - and ....$250!!!! for new Beru wires!!??.......so it seems I'll be going stateside for a tune up kit!! $420 plus taxes for tune up parts on a 20 year old car seems a bit rich!!

Toolmaster

Todzila -

I'd hold off on the tune up - at least for now.

I'd agree that in all probability you have a big vacuum leak - unfortunately it's starting to leak only when you start building boost. It's not the gas at 91 Octane unless it was bad gas, which I doubt. And the injector cleaner - prolly not that either.

A couple things to try:

- open the hood, and check all the hoses under the hood. Play close attention to the blow off valve (that black thing on the J shaped boot right near the turbo) and the Intercooler pipes. There should be a sticker under the hood showing you the routing of all of the vacuum hoses.

- Between intake runners 3 and 4 (towards the back of the engine) and under the intake manifold, is the cycling valve. GENTLY move the three hoses that attach to it with a long screwdriver and see if any broke off of the valve itself. If so - that's the issue.

- If you happen to have a used fuel filter, I can give you a tip - PM me.

- If you're really stuck and want to get dirty - call me (PM me and I'll shoot you my #) and we'll talk it through over the phone.

Good luck!

buxton

I had a leak that was on the bottom side of the rubber connectors from the hard pipe to the innercooler causing a similar problem. Check those carefully. You may want to pull them off and inspect.

xsboost90

sounds like fuel cut- if the wastegate line is split it would do that- could also be the j-boot came off the front of the turbo- it would be trying to pull too much air through the afm to compensate.

Lorax

Check your sparkplugs!

SoloRacer

And forget about the aftermarket plug wires. Many have experience failure with them (me included) and went back to the stock wires. There is nothing wrong with the stock plug wires....and yes they are expensive.

todzilla

I will check out all these things as best as I can..........I guess I'll have to do a search on here for the actual whereabouts of a few things but bottom line, I'll check all my hoses and connections..........would a spark plug be an indication of trouble or are you saying to actually see if one of them is faulty, causing this issue? (Lorax)

.....and Toolmaster, I may take you up on that offer!

Cheers!