Ok i've done a few searches but nothing nails it. Most have been blown engines that have similar symptoms.Car is FC turbo 2.

When it all started:

Driving very hard through contry lanes other night running perfect, left the lanes and got on a motorway pulling about 3000rpm in 5th gear floored it and didn't accelerate. Made lots of noise, boost went up to pressure, but stayed at same speed. Then the rough running became very aparent. So the problem seems to come on in an instant not over the course of a prelonged period

The symptoms:

-Very rough idle
-No power under 3500rpm, hard to pull away and highs gears useless if under these revs.
-Under 3500rpm backfires, spluters, coughs.
- Once above 3500rpm drives normal, responds as it should with all the normal power.

What ive checked:

- Spark plugs, only 6,000 miles old, not brilliant shape but not the worst i've seen.
- HT leads perfect condition 200miles old 10mm items
- coils producing spark
- engine compression tested using normal guage, consistant bonces of 70 psi on each chamber.
- Only quick visual check of vacuum lines.

Things I've thought about but not checked or don't have the kit to check:

- Throttle position sensor
- Timing and timing advance

So what do you guys think? the car is my daily drive and my bicycle is hard work!

 

Did you remove the valve in the compression gauge? That causes the compression to read the same on all rotor faces. Removing it allows you to see the individual compression numbers. 70psi does sound low though... It sounds as though you have a cracked/chipped apex seal.

 

Thanks for the reply.

Yeah did that, isn't that just comon sense!!! If i had one bad seal and two good then one rotor face would still have good compression so a peak compression value is useless to me. I had a mate crank as I watched the guage bounce, constant blips to roughly same psi.

Anymore suggestions?

 

it needs a rebuild. I would do it before it blows up and ruins a rotor and housing if it hasnt already.

 

Uhhhh, shouldn't it be obvious?

You probably have a primary injector clogged or going bad. Secondaries come on, around 3500rpm.

Also, the standard compression testers usually arent all that accurate anyway.

Try switching the secondary and primary injectors, use new o-rings, if it idles fine, then get the injectors, now in the secondary position, cleaned and flow tested. Hopefully you wont need new ones.

Also, do not hammer on the car anymore in this state.

 

Cheers mate. I'll try that sometime this week. Cars sat now till sorted. Time to cycle everywhere.

 

Ok so lets see here a clogged injector huh? Was driving hard and cut out on a 5th gear pull, checks compression and its way low and you think its a clogged injector?? I would honestly quit driving it as its going to blow up anytime.

 

I had exactly the same symptoms on my 88 NA last summer. Took the car out for a late night cruise on some twisties the when I rolled back into town I stopped to pick up some snacks. Got back in the car to head home and it ran like Sh*t up to around 3500 rpm. Over 3500 was ok. I figured vac leak or something goofy. Turned to be one defective primary injector. Over 3500 rpm the secondaries kick in so that's why it clears up the roughness.
Motor had about 500 miles since a complete rebuild with new housings. I assumed the injectors were ok and put them back in after the rebuild.
Big mistake, I should have sprung for rebuilts and saved myself a days worth of work.

Got rebuilts from Rock Auto. about 45$ each and you get 10$ each when you return the cores.
Motor runs better than ever now.

 

Was the engine compression tested with the same gauge prior to this event happening?

 

i had the same symptoms and my engine was blown. i knew before i did compression test but i did it anyways. and the needle didnt even twitch..

rear rotor blown. fucked up everything c/t ( common to ) the rear rotor..

 

did you do the compression check with the engine cold or hot? A warmed up motor is going to have higher numbers than a cold one. If you try it warmed up and still get the same nimbers you're readdy for a rebuild.

 

Just to answer a few questions.

Didn't do a compression test before this rough running started.

The guage isn't mine, borrowed it from a local garage. It's an old knackered thing with smashed glass in front etc, calibration would be a joke, the things about 30 years old.

What i was looking for is uniform blips on both front and rear rotors, and on all the faces. That is what i got! The guage showed consistant Pressure peaks to 70psi at constant intervals. Conclusion is that all rotor faces in both chambers are causing simlar compression conditions.


I have convinced myself that the motor is in a servicable state, but reguardless i'm going to try other posibilities first anyway, nothing like wasting money on a rebuild.

Thanks for all the input guys