Won't Rev. Help!

[wizard124]

I was hoping to be driving, top down, with a smile on my face....but. There are issues

I cant get it to run above about 2500rpm, also some hesitation and stalling.

The engine was pulled about 6 months ago. The timing belt was changed. Seals changed. Changed cam pulleys (matched with originals, careful not to swap them exhaust for intake). Otherwise the engine was not worked on. Head, block, distributor, plugs all untouched. The FI wire harness was unplugged of course and some wires were re-wrapped with electrical tape. Same AFM, throttle plate, injectors, etc.

Idle was rough and at TDC. Advanced to 10BTDC per spec. Engine accelerated poorly and wouldn't rev. So, I took a close look at the alignment marks. Viewing to the front and looking at the marks on the cam housing, it looked that each wheel was off 1 tooth prior to the mark (I would call that behind).

I pulled the coolant T and front cover. Loosened the belt and moved each wheel 1 notch in the proper direction. I used clamps to hold the belt to the aux and crank pulleys so I know they didn't slip at all. Idle is better but she still doesn't want to rev. The holes in the pulleys still don't center in the marks but line up with the driver's side edge on both housing marks. I pulled the #1 plug and compression tested it at 155psi, this is consistent with a prior reading.

At first, I assumed my issues stemmed from the timing belt job. Now, if I move either wheel a notch in either direction, it will be off the mark more than it is now.

I started to look at FI connections and sensors. AFM connector was hit with electronics cleaner and re-seated. AFM door swings freely. Temp sensor in the "T" shows proper resistance. Throttle position connector was re-seated.

I looked at distributor advance with the timing light. It advances up to the point of the stalling then while the engine is missing, it retards a bit. It a symptom or the cause

Tomorrow, I will check fuel pressure in the manifold. But, my gut tells me my problem is with the cam timing.
Help and suggestion are welcome

[So Cal Mark]

your ignition timing shouldn't retard when accelerating. Have you connected a vacuum gauge to the manifold to see what the vacuum is at idle?

[DanD]

Most common cause for your symptoms would be a clogged cat. Bad cam timing can help kill a cat BTW. Long shot might be throttle position sensor. Unplug it, and the car should still run, maybe better. Nothing blocking the AFM or intake ?

Do you still have your original cam gears ? What was wrong with them ?

[GeorgeT]

Also check the magnet pickup wires under the distributor plate. They will fray over time and give problems when the plate starts to move under acceleration.

[narfire]

Here's another guess.... check the grounds for the injectors (two wires) are attached well to the intake plenum.

When idling, can you manually get the engine to rev past 2500?. Does the cable allow the butterfly to open all the way..

Being one tooth off will not offer best performance but car will run and will rev higher than 2500 rpm.

[wizard124]

your ignition timing shouldn't retard when accelerating. Have you connected a vacuum gauge to the manifold to see what the vacuum is at idle?

I have 17 inches at idle. As the RPM increases, it reduces to almost zero as the engine bogs down.

Here's another guess.... check the grounds for the injectors (two wires) are attached well to the intake plenum.

When idling, can you manually get the engine to rev past 2500?. Does the cable allow the butterfly to open all the way..

Being one tooth off will not offer best performance but car will run and will rev higher than 2500 rpm.

I re-seated both grounds. They were tight to begin with. I can manually open the throttle to full.

Also check the magnet pickup wires under the distributor plate. They will fray over time and give problems when the plate starts to move under acceleration.

I took off the cap. Wires are not frayed. I used a vacuum pump and observed the plate move.

Most common cause for your symptoms would be a clogged cat. Bad cam timing can help kill a cat BTW. Long shot might be throttle position sensor. Unplug it, and the car should still run, maybe better. Nothing blocking the AFM or intake ?

Do you still have your original cam gears ? What was wrong with them ?

A vacuum test diagnostic chart I have seems to point to a clogged cat. Mine was replaced to pass smog less than 4000 miles ago. I haven't tried unplugging the throttle position sensor. The intake and air filter were removed and replaced but worth a look. I had spare lighter/spoke cam wheels that I put on.

Some other tests I did this morning. The fuel pump maxes out at 38 psi when cranking and holds 30psi in the rail when running. When I disconnect the vacuum line to the regulator the pressure holds at 38. The car still displays the same symptoms when I try to rev up.

I have good spark jumping from the cap to each wire. I twisted the distributor as I accelerated the engine. Advancing or retarding produced the same symptoms.

[majicwrench]

Easy way to check for plugged cat is to drill 1/8" hole in exhaust pipe (ahead of cat) OR in EGR pipe (if you have egr) Then a cheapy vac/pressure gauge with short nipple of vacuum hose. Typical good cat will show just a lb or two of backpressure. A cat plugged enough to create issues like you have will exceed 10 lbs pressure. Even wo gauge, good cat will just gently pis gases out of hole. Bad cat will blast a stream of high pressure out. Easy to see difference.

That said, hard for cat to plug w car just sitting there. In my neck of the woods, packrats get into things like exhaust pipes and fill em full of dog food when rigs sit too long.

Test exhaust backpressure, just takes a few minutes, then you know.

[azruss]

My 80 has a plug just before the cat. Take out the plug and it will tell you immediately whether the cat is plugged.

[wizard124]

Easy way to check for plugged cat is to drill 1/8" hole in exhaust pipe (ahead of cat) OR in EGR pipe (if you have egr) Then a cheapy vac/pressure gauge with short nipple of vacuum hose. Typical good cat will show just a lb or two of backpressure. A cat plugged enough to create issues like you have will exceed 10 lbs pressure. Even wo gauge, good cat will just gently pis gases out of hole. Bad cat will blast a stream of high pressure out. Easy to see difference.

That said, hard for cat to plug w car just sitting there. In my neck of the woods, packrats get into things like exhaust pipes and fill em full of dog food when rigs sit too long.

Test exhaust backpressure, just takes a few minutes, then you know.

More experimentation.

I removed my O2 sensor. Ran the engine with the same results. Fuel pressure in the CSV line reads 30psi. I crimped off the fuel return line running from the fuel pressure regulator. Pressure spiked above 40 and I was able to rev the engine

It is looking like my PR is at fault. Once she cools down, I'll replace the O2 sensor and have another go at diagnosing this problem. I have the manual so I'll follow it closely. It doesn't list a spec for fuel pressure in the rail at idle but my notes from an earlier test says I had 29 psi at all rpms (back when it was running well)

[wizard124]

I am back to thinking it is my valve timing
The belt and cam wheels are the only changes or adjustments I made during the lay up.

My PR tested perfectly. Unhook the vacuum line, operate starter. The pressure settles at 35 psi. My manual specs 35.25. I can't read it that closely. Run the pump and there is good volume. The fuel delivery system seems to check good.

Can the ignition be cutting out at higher RPMs? That's is a system I need to read up on. Coil wires are all tight and re-connected exactly per my notes. Other ideas

[RoyBatty]

Would you like a second set of eyes to help you with the cam timing?
I am free tomorrow and willing to make the jog your your way to help out.

[wizard124]

Would you like a second set of eyes to help you with the cam timing?
I am free tomorrow and willing to make the jog your your way to help out.

Wow! That is quite an offer. I have 2 little league games so my day is too broken up to take advantage of your offer.
However, If you could take a look at your cam timing (certainly less time than your offer) and describe the alignment marks on the cam housing relative to the holes in the pulleys at TDC. This would be looking forward at the backs of the pulleys. This will give me an idea of which way I may need to go. Try to be as precise as possible, 1 tooth off is not much in either direction. Can you test your intake manifold vacuum at idle? That number would be helpful.

Since my last post on this. I inspected my plugs (all good with a light brown burn). I compression tested each cylinder. They were all close and maxed out at 170 - 174 psi.

I also ran through the Breakerless Ignition diagnostics in the Brooklands manual. Coil and control module were all in spec. I re-set the rotor to pick-up coil gap for good measure. Cleaned all contacts.

Fired it up with the same results. This is really bringing me down

[So Cal Mark]

17" of vacuum would indicate the timing is okay. Rather than drill holes in the exhaust, merely loosen the bolts at the flange. That will allow enough of a leak to determine if the catalyst is plugged

[RoyBatty]

PM me for my cell number. Let's discuss this.

[wizard124]

The saga continues......

I had a long conversation this morning with a fellow forum member. I re-played it from the first act. He suggested that I should concentrate on the injectors.

I re-checked the injector ground at the inside left ground post. Re-checked the connections off the right rear cam cover.
I pulled each injector plug. Voltage was the same in each and fluctuated during cranking. I tested the resistance on each injector; all were in spec at 2.3 -2.4 ohms. I sprayed electronics cleaner into each plug before re-connecting them. The engine is still running poorly. I added some fuel injector cleaner to the fuel. At this point, why not

Next step is to pull each injector and check for fuel spray. Or, pull the cam covers and look for damage and tappet position at TDC. Or, re-set the cam pulleys a tooth at a time to see if she runs better. Yikes, what a PITA!