So I posted a thread about a month ago about my 1990 RS 5.0 running like dookie.

Symptoms were: loss of power, rough acceleration (shaking on acceleration) small backfires on deceleration.

Distributor had too much shaft play. Got a good yunkyard distributor, replaced ICM (thermal compound), Pickup, cap and rotor, and ignition coil. All parts Delphi, cap and rotor Accel. Added another washer to the gear to get rid of vertical play. Car also has new plugs, wires, oil, filter, trans fluid. Less than 200 miles ago.

Got the distributor in, set timing by ear.. Idle was high but fine while warming up. car went into closed loop, idle dropped to normal, idle was smoother than ever.*

Test drive:*every problem mentioned above came right back as soon as I pulled out of the driveway.

The metal hose from the bottom of the air cleaner to the exhaust manifold broke and cant reach the manifold. It broke right before my car started acting up but i cant see that having such a dramatic effect. Could be wrong.

Im at a loss, any help on where i should begin looking next is greatly appreciated.

 

Never a good thing. Use a timing light.

Sounds like you either have a plug wire incorrectly installed or a possible vacuum leak.

Firing order is 18436572 clockwise. It's very easy to get 5 and 7 mixed up.

Get a propane torch. Unscrew the nozzle end and put some rubber hose on it. With the engine running and the propane turned on slightly, run the rubber hose along the base of the carb and along the intake manifold. If you have a vacuum leak, it will suck in the propane and the idle will increase.

 

Im gonna buy a timing light and a torch right this minute.

I drew up a little reference picture of where each plug wire went before pulling them out. im going to double check right now though.

Is it possible I installed the distributor gear a tooth off? I made a mark where my rotor was pointing and a mark to realign the distributor. The marks are the same color and close together. Maybe I got them mixed up when I reinstalled the distributor? But wouldnt my car run way worse if I were to do this?

 

Didnt have a chance to get out there tonight but did a little reading. I take back my question about the distributor being a tooth off, found out it doesnt matter as long as base timing is achievable.

I also take back my question about the broken metal hose. Found out its actually not connected to anything.

Tomorrow I am going to properly set timing, check my ignition wires, check my vacuum lines and do that propane test, and give my fuel injectors and fuel pressure a look. Will post followup tomorrow after work.

 

If you haven't replaced your fuel filter in a while, I'd check that its not dirty. Fits all your symptoms.

 

Never really an issue but it could be a fuel pressure problem. Maybe not really a pressure problem but a lack of flow.

Many years ago, I field repaired a 70's chev 4x4. After going through some brush, they had a lack of power. Ran good at an idle but had no power. Ended up that a branch got up and bent/crimped a fuel line. Not enough to kill the engine but enough to restrict fuel flow.

From your symptoms, I'd still go with crossed plug wires and incorrect timing.

 

I set the timing yesterday, runs alot better but still shaking and runnng rich.

I checked the wires, they are all in order. Also checked vacuum, everything plugged up correctly, though i did not do the propane test

Checked my engine codes as well, came back with coolant temp sensor, low voltage to fuel pump, system overvoltage.

Will replace cts after work, probably the reason its so rich, gonna grab a new fuel pump relay as well, gonna take my new alternator back as well, i thought my gauge pegged since i put it in but it may im fact be running at 18volts

 

Now that you have a timing light, connect the inductive clamp onto each plug wire and see if the timing light fires. That can tell you if all the plugs are working or not.

 

Great idea! I tried pulling each wire while the car was running and ended up shocking myself and giving up. Ill do this when i get home.

Last night i started the car cold, it idled perfect, once it warmed up the exhaust made a misfire sound, a bit later it made another, then a bit later it became constant and my car began to sound like a putt-putt again.

 

I dunno how long ago the previous owner changed it, ill add that to the shopping list when i grab a CTS and fuel pump relay tonight

 

All cylinders are firing according to my timing light
Replaced fuel pump relay, starts a bit quicker now
Replaced CTS, its not running as rich now
Discovered the thermac valve was stuck and blocking the intake. I removed the entire Thermac assembly and plugged the vacuum at the throttle body and at the air cleaner
Tested alternator and battery voltage, 14.7V. Really high for a brand new battery and alternator
Cleared codes and test drove.

It ran pretty good under all driving conditions.
Didnt feel any misfire. The ignition seems to be doing a great job.
Some power has returned as well.
all the problems its been having are pretty much gone except for the shaking under acceleration and still missing a bit of power.
In fact, I'd be very impressed by how good its running if it werent for the shaking under acceleration.

Time to start playing with fuel

 

Got under my car last night. Been working 12 hours a day for 7 days a week since christmas so havent had much time.

Anyways, last night I fired the car up, its having random hesitations when idling, drove it around the block, still shaking when accelerating.

Got a can of brake cleaner and sprayed around the intake manifold, throttle body, and vacuum hoses. Not a single change in the idle.

I did notice the driver side fuel injector is spraying a tiny bit less than the other and the spray pattern is a tiny bit narrower. Planning on pulling them both and running injector cleaner through them as well as give them all new gaskets orings and filters.