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Discussion Starter · #1 · (Edited)
My '75 99 is running very poorly. I need help!

It starts a little rough and idles normal, but when you rev it backfiring occurs in the intake system. You can get the backfiring to stop with an extreme rich mixture. In either instance it revs slowly and has no power when driven.

I have replaced the metering plate, fuel distributor, and warm up regulator with no noticeable difference. Every problem I have had in the past has been solved by doing this, so I'm stumped. Furthermore, every part that I've taken off this engine is in amazing condition!

The fuel injectors spray nicely, the fuel pump output when measured on the return line is over 900 mL in 30 seconds. The ignition timing is at 17 degrees BTDC with the advance vacuum line plugged.

This injection system was mainly 1978 components when I got the car. The stuff I've put on are 1987 components. There is a modulating valve in the loop but it isn't powered.

Any ideas are appreciated!
 

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i personally know nothing about cis, but the guy that works in the bay next to me (a saab mastertech. of 21 years) does. i had him read this and these were some thoughts:

-check condition of points and check dwell.

-have you had the distributor out? if so, is it possible that it's a tooth off? he said this really sounds like more of an ignition problem than a fuel problem and that he has seen cars with your exact symptoms that had the dist. a tooth off.

-cam timing a tooth off? that might explain the lack of power and backfiring into the intake.



good luck!
-ethan
 

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Discussion Starter · #3 ·
There are no points because its a hall effect electronic ignition.

The distributor has not been out of the car.

The cam is not a tooth off.

Thanks for the ideas though! DeLorean suggested I try and run it with the exhaust off, as it may be clogged. I removed the exhaust the other day but haven't started it yet. If it's not that, it probably is an ignition issue.
 

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Well, I will spit back what you suggested to me...keep turning the meter plate/mixture adjustment. That's all I got, even though I'm sure you've done it already. It took my FOREVER to get mine running correctly by tuning that thing, but I got it eventually.
 

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if u get it running right like that, perhaps you should just leave the exhaust off :):)
 

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It could be the coil getting weak, or a bad coil wire. We've seen this before. I know this is grabing for straws but try cleaning the grounds on the battery box and transmission. And with the modulating valve not working you are going to have to run it a little richer.
 

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Discussion Starter · #7 ·
I am now thinking spgproject had it right with the distributor being off. I noticed when I first got it that it is at a different angle than I have seen before. This could be due to the fact they retimed it so the timing is in fact correct, but it's not getting the full length of signal from the hall sensor.. I imagine this is what dwell is.

The car was fun to rev with no exhaust but the fact that it won't rev right and still backfires, this time out of both manifolds, took some of the fun out of it. :)
 

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Discussion Starter · #8 ·
Normal B Motor:



My B Motor:



As far as I know Jesse's car is timed right, and I just checked mine at 17 degrees, so there should be a max of 3-4 degrees difference in BTDC timing in these two motors, and that should not be discernable in this picture. Yet we have a huge difference.

Thoughs?
 

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definitly looks out of place.
 

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my brown 99 was that way and it ended up being a severly plugged cat.
 

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that was my thoughts, however it seems he verivied that was not the issue.

and yeah that distributor. something is fishy there.
 

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It's the same distributor, paul. You can swap them.. only difference is the gear on the end of this one, and the 16v one hooks to the cam.
yeah but on the 16vs its impossible to install them wrong. seems as if its quite possible with the b-motors eh?

Paul
 

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Discussion Starter · #17 ·
It appears the problem is fixed.

At first I thought he had the spark plug wires on but by now i've forgotten how they were and all I know is they are right now. Also, I think he has a flywheel from a 900 or something because I believe the majority of the problem was the timing was not advanced enough. If you extend the marks on the flywheel out with your imagination, where I have it now should be 50-60 BTDC...

Revs great, idles good, (a little high like I like it), running nice and rich and I can't wait to drive it tonight. I'm already practicing tuning out the sound of the wheel bearings by making a thumping noise with my mouth when I walk. :)
 

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the flywheels can easily be installed incorrectly, making the timing marks about 45 degrees off if you are off by one bolt.

I'd suggest removing the clutch cover, and your #1 spark plug. bring that piston up to TDC, and check the timing marks. Once you verify that it is not right, just have to remove the clutch, put the flywheel on correctly, and re-install everything and re-time it.
 

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Yeah...I had the flywheel on one of my cars off by one bolt. It made it very difficult to figure out why the car was running like crap :lol:
 
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