iMurias

Hi, Hoping that some light could be shed onto all of this. I am experiencing a few problems, and am actually thinking that they might be linked somehow.

I have an '88 S4 convertible.

When I first got it all was great, 17mpg in city and 23-27mpg on highway. I have it just shy of 6 years, put a bit over 60k on it, and it has a total of just shy of 192k (original engine). Compression on this engine has not changed since I purchased vehicle, low 100's. Now I am lucky if I get 13mpg in city and 18 on the highway.

I have a list of under the hood symptoms, which I am thinking at least a couple of them are related:

1) runs incredibly rich, smell of fuel almost noxious at startup (hot or cold), at idle, even while driving can smell the unburned fuel.
2) serious difficulty in starting, regularly floods, hot or cold, may take over 9 seconds for it to start, this issue has been getting worse the longer it goes without fixing. Always cloud of unburned fuel when starting.
3) occasionally while warming up the RPMs may have a life unto themselves, bouncing up to about 2500... My foot nowhere near the pedal.
4) while cold if I get into the gas, it will puke all over itself at around 3500. Now when car is up to temperature.
5) at any temp, if between 2500 and 3300, and I just want slight gradual acceleration the car hiccups slightly

I do have a cracked exhaust manifold, and have never replaced the O2 sensor since I have owned the vehicle. I do have a replacement manifold and new sensor.

Bit of background:
When I got the car it was great.
Two years ago I replaced the TPS with a new one, and it still checks fine, and I keep it dialed.
I do not remember if this is normal, But I noticed that there is no trailing spark at time of initial ignition, only once the car is fully running.

Year and a half ago I took it to a mechanic, for very similar symptoms. He replaced the mass air flow sensor with a used one, and told me the reason it was puking all over itself was because of either the thermowax, or a part near the thermowax which was involved to get to and not to worry about it until something else went bad down there.

The problems all came back, the same mechanic no longer wishes to work on the old RXs, so I took it to another. This one cleaned my MAF as it was really dirty. That only helped a small bit for a short time, then all came back. The cleaning never helped my gas mileage return.

Aside from the richness, and slight hiccup, the engine when warm, runs exceptionally well and smooth. My dad has a 91 s5 convert which purrs, and he thinks mine is comparable to his when mine is warm.

I have done a great deal of reading on this site, and sometimes one can read too much, and not gain a clear picture. So I ask for help, as I don't really have time, but I think I have more time than money at the moment.

Anyone have any thoughts or insights? Any would be greatly appreciated.
Thanx

Murias

RotaryEvolution

iTrader: (30)

i think your mechanic meant coolant temp thermosensor, however it isn't difficult to change even without removing the manifold. the issue usually isn't the sensor though, but the connector for the thermosensor.

hesitations are usually fuel pressure/volume related, dirty pump sock or fuel filter up front. also normally caused by bad grounds from the engine to the ECU or from the battery to the engine.

O2 sensor might help your mpg, but it doesn't explain poor city mileage, only slightly highway.

flooding, could point to the coolant temp thermosensor or to fouled plugs, or to a bad AFM(don't trust that a replacement is good).

trailing ignition does not fire during crank.

another more rare issue is the fuel pressure regulator diaphragms beginning to tear on these cars due to age and dumping fuel into the intake runners through the vacuum line.

patrickm

interesting the piping going around the shock towers. Never seen that before.

rotaryengineer

Classic n00b move - scrolled down to far - replied to wrong thread.