FFCam1991

iTrader: (4)

Hey,

I have a problem with my 305 TPI and it goes something like this: cruising between 1,000 and 2,000 in any gear, but especially the lower ones will cause a horrible knocking in the engine (or elsewhere...?). This probably isn't even a "knock" in the normal sense but that's how I would describe it, the car jerks back and fourth and makes a "chugging" noise. I have a new O2 and Coolant Temp Sensor.

I just replaced the spark plugs, wire set, cap and rotor. Am going to recheck those tonight. I will also check my timing once I buy a light. In addition, I have a Service Engine Soon light that keeps popping up after the engine has been running for about 5-10 minutes. Sometimes it will never come on. Other times, when you stop at a light and go again, the light will turn off. I'm going to order a scanner to check this too.

Any ideas as to where to turn? The car used to have a pretty wicked misfire under acceleration but I think the new wires/cap/rotor helped alot. It accelerates smoothly with good torque.

My gas consumption is also brutal. It seems to really suck it back when the light comes on. I don't know where to look next.

Thanks for any suggestions!

FFCam1991

iTrader: (4)

Anyone??

My gas consumption is seriously like 10-15 mpg, I used to get 26 mpg highway (imperial)!

kevmann

I am not a mechanic but check the codes. There are threads on how to do that. Sounds like TPS off the top of my head but all you can do is guess until you check the codes.

ls six

Have you checked timing at all? When you did the cap and rotor was there a lot of corrosion inside the disty?

Also the 90-92 injectors tend to leak badly after a while. My 90 would barely start and run at idle and would buck and surge at low RPM's but pulled good at higher revs.

Essentialy the extra fuel would cause the car to run drasticaly rich at low RPM's, but at higher RPM's the added fuel made up a smaller percentage of the charge ( more air at high revs but the leak stayed constant) and the problem became less apparent.

If you can borrow or rent a fuel pressure guage and check to see if the pressure falls after the pump primes the system it'll take 5 minutes to discover the proble. Just turn the key to accesory's and watch the guage.

FFCam1991

iTrader: (4)

Hey guys,

Thanks for the ideas. I thought TPS was a possibility as well, after being suggested by a co-worker who is big into cars (Corvette owner). But I went to NAPA and on two different occasions, two different people said I was barking up the wrong tree with TPS. I'll be able to scan the codes probably next week.

The cap of the distributor looked fine to me, the rotor had a ton of black marks on it (carbon?) and yes the base was pretty damn rusty.

I have a set of Bosch Design III's coming in the mail, I hope they will provide a lot of improvement. Should drop em on this weekend.

Timing will be checked tomorrow or the next day...I have the light but just need to read up on how to go about it. Can you manually adjust the timing or does it have to be done electronically through the ECU?

Just tested the fuel pressure. Turned on the ignition and there was no reading on the tester. Fired up the engine and it held steady at 36 PSI. Turned off the engine and it went up to 42 PSI. These are all well within range according to my Haynes manual...only thing I can't figure out is why it didn't jump when I initailly turned on the ignition. Am I correct in ruling out the fuel pump and FPR because of these readings?

Car sounds like crap and smells about as bad. Its backfiring and just generally nasty.

Thanks for the help!

kevmann

Sounds like you are heading in the right direction.. Good luck

shanewbenson

you should be able to check the codes without a scanner if you have a 12 pin Assembly Line Diagnostic Lead. Just insert a paper clip to jump pins A and B which i believe are the two top right pins. With them jumped turn the key to on but dont start the engine. The SRS light will flash and just count the flash order cause thats your code. Here is a good site http://www.automotiveforums.com/t679458.html

crmmaj9

The last time mine did that it actually turned out that the fuse for the fuel injection had blown. I still can't believe it was running at all but it was!!! Check them before you spend too much money on it!! Hope it helped...

FFCam1991

iTrader: (4)

Thanks for the suggestions,

Would blown cats have any effect? I think the horrible exhaust note is coming exclusively from them. I think an engine running excessively rich can wreck the cats? Never really gave much thought to this before but now that I think about it, judging by the noise, there HAS to be a problem.

ls six

If the cats are blown as in the catalytic material is gone then yeah it'll be louder. I wouldnt say it would be an un plesant sound though. A lot of people on my Mazda forum gut stock cats for better flow but with out the raspiness of typical imports. On our cars it makes for a nice mellow deep sound.


If the cats are clogged (typical from running rich or with the wrong fuel) or fused (from excess heat) then it'll cause all kinds of problems, but you wont notice any noise and the main problem will be the car falling on its face at WOT or high RPM.

My gf's sisters car just did this, one of the FOUR! cats melted and the truck topped out at 55 and was slugish if you gave it any kind of pedal.