Low power, smoke, backfiring

[Zero Signal]

After having no motor for 5 years and installing a junkyard motor this summer, my car is finally officially on the road, registered (past emissions somehow) and most of the kinks have been worked out. Now it's running cool, idle is stable, there are no leaks anywhere since all the seals are fresh and it's reliable enough to use as my daily driver once again.

Now, the last issue with it, is that it feels like it's about 30-40hp low on the top end. It has gobs of torque to about 2500 rpm and that's it. The torque just seems to flatten out and drop off quickly past that. The engine is trying. It sounds like it want's to go fast, but it just isn't there. Here are my symptoms:

• Low power over 3k rpm, the car just doesn't pull like it should.
• Some greyish smoke in the exhaust when I punch it at around 2500-3000 rpm.
• Pinging at WOT, but not in CL.
• Some occasional backfiring on tip-in, just as I change gears and start to gas it again.
• MAF Sensor is clean
• Spark plugs are Autolight 24s (IIRC)
• Coil and distributor are new
• Fuel pump and filter are new
• PCV valve is new (but I had to remove the filter)

I have no codes, and the motor is basically completely stock. I have a TwEECer, so I may try to look into it that way.

I ran a couple cans of Seafoam through it and is helped a tiny bit, but it was no magic bullet.

Could this be a bad head gasket? I never did pull the heads.

Thanks for any help!!

 

[BlackVert]

Good to hear it is back on the road!

What tune do you have in there now, T4M0 (GT) or J4J1 (Cobra)? The J4J1 is reported to be better from a pinging standpoint. IIRC, the MAF is the same between the GT (T4M0) and Cobra, but the Cobra (J4J1) has 24# injestors, so that is all you should have to change to use a J4J1 in a GT.

 

[HISSIN50]

There are about a zillion things...............
Starting easy: Given what you've been up, are you sure the SPOUT connector was reinstalled?

 

[Zero Signal]

Thanks fellas. Yeah, spout is installed and the base timing is dead on 10°.

The cap & rotor are in ok condition too. The spark plug wires seem alright as well, but those can be deceiving. The engine grounding straps are new and the connections are fresh.

My ideas for the potential problems:
Bad head gasket
Oil through the PCV valve
Bad valve guides (seemed tight enough when I checked them before installation)
Bad/obstructed injector(s) (seems unlikely)
Bad TPS
Malfunctioning EGR

Right now the tweecer is just turned off, so it's T4MO. I didn't want to mess with it until the car is running optimally without it. I used to pull a few tricks to fix our 94-95 pinging problem, but for now I just want to make sure I'm not bandaiding any real problems. Besides, I think I'm gonna sell the tweecer since I plan to keep the motor stock(ish) anyway.

 

[revhead347]

Oil through the PCV could definately do it. Doesn't sound like a head gasket to me. Pull the spark plugs and see what you find. What are they gapped to? I think stock is around .052". Might want to try to gap them down to .040" and see if that helps any. It might just be blowing out the spark a little on the top end.

Kurt

 

[Zero Signal]

Good idea, I'll try that. I think I gapped them to spec per Haynes, so .052".

 

[toyman]

You said no codes but did you mean no CEL? I would leave the plugs gaped at spec of about .054". I would also test the TPS voltage range. If the volts aren't moving smoothly from about 1v to 4.5v the PCM doesn't know that the throttle is physically opening. If that tests okay verify the MAF signal volts.

 

[seijirou]

I don't think you have a headgasket problem but it's not impossible. Have you noticed any oil consumption?

Burning oil can cause this problem but in my experience you don't push any significant oil through the PCV unless you've got some nasty blowby because something is wrong. Personally I would just pop out the PCV and take a look, if it's dripping with oil, do a compression check. Also take a look at your oil dispstick, is it seated in the tube or did it pop out a little bit?

If you've got bad valve seals, it will puff obvious smoke on startup and then clear up. Let the car sit for a day, and then have someone else start it while you're behind it looking at the tailpipes.

Blowing out the spark just isn't going to happen unless the plugs are fouled.

Have you cleaned the MAF yet?

 

[revhead347]

I've had trouble with the factory gapping before. I find it works better with a gap of about .042" I've got to run it down to about .032" if I spray over 100 on the engine.

Kurt

 

[HISSIN50]

Without the filter under the PCV valve, burning some oil is not out of the ordinary.

The stock ignition should be able to handle 400 hp NA if healthy.
New parts are not necessarily good parts. If you have an old coil, I would try it.

Are you sure the timing is actually advancing?

 

[revhead347]

That PCV valve filter is dirt cheap. Any reason why didn't reinstall one?

Kurt

 

[Zero Signal]

I didn't know you could replace it. It was surgery getting the thing out int he first place, haha.

I may have to break out the laptop and do some datalogging to check the timing and sensor stuff. I'm not completely sure the timing is advancing, but I suppose I could do a small test with the timing light with and without the spout and some throttling.

 

[HISSIN50]

The filter (often called a breather) might be stocked at the dealer. Resto houses (i.e., LRS) sell it and Checker might (they used to).

Yep - just connect the timing light and goose the throttle a little. The advance will skyrocket since there's no load on the engine.

 

[revhead347]

You just take a magnet it comes right out. It's designed to be changed on a regular basis.

You can get a breather element at any auto parts store, they are like $2.

Kurt

 

[revhead347]

Sorry, $5.

Advance Auto Parts: Crankcase Breather by Purolator - Part B15231

Kurt

 

[Zero Signal]

Hah, close enough on the price. I'll pick one of those up. I still feel stupid not knowing it was replaceable. I was thinking I would also put together an in-line oil separator too, just because I like the idea.

 

[Zero Signal]

Discovered/developed a mysterious coolant leak on the way to work this morning. I can smell coolant and see some steam (it's cold out) coming from the back of the engine somewhere. It's not coming from any hoses and it's not pooling up on the lower manifold. I think it's time to check the oil for water. There were lots of bubbles coming from the radiator cap into the overflow bottle, so the system is being over-pressurized with air. I'm starting to think head gasket.

 

[seijirou]

There were lots of bubbles coming from the radiator cap into the overflow bottle, so the system is being over-pressurized with air. I'm starting to think head gasket.

Yup

 

[Chythar]

Yup

X2. Your head gasket is blown and letting exhaust into the coolant. Had this happen to my old V6 twice. Time to tear it down and find the carnage.

 

[Zero Signal]

I knew I should have replaced them while I was doing all the other seals I'm just trying to decide whether to drive it 20 miles home after work today or call a tow truck for $90.