I am getting poor gas mileage (8-11), experiencing hard shifts late at high RPMs, slight erratic idle, and a top speed of 85.

I just replaced the TPS and IAC (minimized the erratic idle) and a 02 sensor and have an EGR on order. The fuel injectors were replaced 10K ago.

After replacing these parts, I have not received any error codes.

It starts fine but makes a noise similar to a diesel engine when accelerating hard.

Could this be the torque converter, EGR, vacuum leak? Any ideas would be helpful. If it could be vacuum related, is there a good way to check for leaks. I've tried feeling lines and using soap water to look for leaks, but with no success.

 

This is a good place to find answers to your problems. You said your injectors were replaced 10K ago, did you have the car then or was it done before you got it? I have an 85 and average over 20 mpg, you definately seem to be having a problem! What do your plugs look like? Are you burning any oil or is your coolant down? Vacuum leaks are not just in the hoses, I found mine was the intake manifold gasket. I only had 40K on the car and the 8th cylinder was fouling. I noted the smell of coolant and it would sometimes drip but not always. It turns out the intake was loose, when it was taken off some of the torq bolts could be turned out by hand!! This caused oil to be sucked into the intake for the 8th cylinder. The coolant was leaking up through the intake bolts on top of the intake manifold. Thank heavens it wasn't leaking into the crankcase! The guy who diagnosed and fixe mine said he had had one in with the main bearing frozen because the coolant had corroded it after it had gotten into the crankcase. I'm not much of a mechanic but this was a big problem for mine. It runs great now though. What size injectors were put in yours when replaced. If they were accel 24# they might be running too rich since the OEM is 22#. All the catalogs say the 24s are the correct size but they aren't!! I'm wondering if you still have the original injectors. I need to replace mine and I want to get some used ones to rebuild. You'll also get other good council from the group. Good luck

 

This is a great place to find answers. I had a dealer replace the fuel injectors. I do not have the old ones and have no idea was size the new ones are. All I remember is it was a hefty bill! Is there a way to check?

I pulled one plug out and it looks good. The plugs and wires were replace 15K ago. Don't know about the distributer cap though.

 

sure you adjusted TPS correctly? I would double check it. Some time it's the easy things that gets us

 

I am sure the TPS is correct. I even bought a new gage to double check it. I have .54 volts idle and 4.49 WOT.

I forgot to mention that I have a vibration during acceleration as well.

 

Actually the 85's had 24lbs injectors not 22lbs.
I am putting mine into my garage next week for some much needed work for next year to take to the track finally.
Even if he is running too rich, it won't get such bad mileage as he is getting. I was running mine for a while waaay too rich, which hurt performance, but not as much. I was getting 16miles to the gallon then. (And that was with a going Fuel Pump too)
This week I'm replacing the Fuel Pump actually with a higher duty one.
If you get bad performance, mileage, I'd say do a major tune up, check your fuel pump and fuel filter, as those should be changed anyways by now.
After, I'd check my Catalityc Converter out. Few years back I had symptoms JUST liek yours, it even stalled sometimes at idle, and it was a Cat that was a brick.

Good Luck

 

thanks for the info. I'll replace the fuel filter first, then check pump and on to exhast. Do you think I should waste my time with the EGR now or check these other things first? The EGR looks like a lot of work.

 

I have just replaced the EGR valve and havn't noticed any improvements yet. So far I have replaced the EGR, O2 sensor, TPS, and IAC (plugs, wires, and injectors not long before).

Tomorrow I will replace the Fuel Filter. If this doesn't do it I am going to check out the Catalityc Converter. Any other Ideas? I am not getting any codes.