Sputtering from start

Hey guys. I posted this question a few months ago but still haven't solved anything. My '91 5 speed is sputtering, mostly from stops but occasionally in 2nd and 3rd too. When it catches the power is great but I do have to play with the gas to do it smoothly. I have recently (last 3 months) replaced the 02 sensor (bosch) the fuel filter, fuel sender, and alternator. I blew a head gasket almost two years ago and got a lot done then (cap, plugs, wires etc.) but I feel the problem started when I got it back from the shop. It's not so bad that it's not drivable, but it's pretty annoying and not a fun as my 5sp should be.

Of note is that when I take it from the coast, where I live usually to the mountains (6k altitude) the problem seems way worse.

My mileage has also dropped.

Any ideas? I have read as many posts as I could find here on Naxja, and still looking. If you know of any good threads, let me know.

thx y'all

TJ

Hello, I see you've not received any responses yet. This is my first post here so take it for it's worth.

Have you cleaned out your throttle body and TPS? This sounds like a likely culprit to me.

Yes I have done both of those things. Any other ideas? It's still driving me nuts.

Could be a lot of things.

A bad O2 sensor or the wiring could default the PCM into a rich mode. It may sputter until the rpm's come up.

Something with the MAP may also make it run rich. Most often it is something with the MAP vacuum.

Weak spark may also make it run crappy at lower RPM's.

Low voltage to the CPS, syns sensor (and other sensors) may make it run crappy at lower RPM's. Many sensors share a common 5 volt (sometimes 7 or 8 volt depending on the year) sensor in voltage. One sensor gets a partial short (low resistance) and it affects the others.

The orange wire is usually the in voltage or the CPS, sync sensor and maybe the speed sensor. Other sensors my be a violet/white wire, voltage in wire. I'm guessing here, I don't have a 91 FSM.

Timing may also be an issue, either the distributor is off one tooth or the TPS isn't working right.

If you had a head gasket issue you may want to check your compression. A serious vacuum leak or very low compression in a cylinder can screw up the exhaust oxygen content and cause the O2 sensor to give faulty data to the PCM. Depending on the severity of the oxygen in the exhaust being off, sometimes it causes erratic idle or sputtering at lower RPM's. It may cause the idle rpm's to cycle from a little low to a little high or induce an idle miss.

Swapping out the sensor may not cure a problem if the connector is oily inside on the pins or if the connector is coolant soaked. We are talking about very low voltages here and low voltages don't pass through resistance (dirt,oil or corrosion) well. A poor connection a the connector or a bad wire is as bad as a faulty sensor.

If I had to venture a wild guess I'd say your front O2 sensor has an issue or the rear O2 sensor wire is cooking on the exhaust. Maybe your O2 sensor heater fuse is blown. Or maybe the O2 harness where it comes up from the motor on the drivers side through the power steering bracket is cooking on the exhaust manifold or damaged some other way.

Have you tried the key method for testing the stored codes yet? The engine trouble light won't light for a bad O2 sensor, but the PCM will store a code if the O2 sensor is toast. It won't show any code if the O2 sensor is partially failed.

Look and see if the magnet has come loose for your sync sensor in the distributor.

Look and see if your CPS is oil soaked.