Some bugs: bogging down

[Lex]

Aside from the starting issues I am having with the GTX, I also encountered another strange issue. Yesterday I drove it pretty hard up a hill. At the end of the hill, I slowed down but I was still in a high gear. I believe I was in 4th and doing 35 mph. I step on the gas a little and the car bogs down and lurches forward in a really weird fashion - so I slow down some more and crawl to a stop. My EGT's while going up the hill did not go over 1150F. I stopped the car and let it idle and cool down. I then started driving again and drove just fine - pulled like before and did not bog down.

What could have hapenned? I am running the NA ECU at stock boost with GTX injectors, an RX7 VAF and a Walbro fuel pump. Could that bogging down be running lean - why would it run lean at part throttle and low RPM? My car smells really rich at idle. Could it be overheating? My EGTs do not seem extreme and my temp gauge was not out of the ordinary.

Later that night I pulled the plugs and valve cover. The plugs looked ok (although a little too white) and everything looked well inside the valve cover.

If I am running lean and detonating, is the bogging down a result of it? How can I tell if I detonated? (are there any signs on the engine that are easily visible) I hear no pinging from the engine even under load at a low RPM in a high gear.

Some input from you turbo experts would be great. Thanks.

[ROB-80E]

I would have said it didn't get fuel too....but when it comes you guys running non GTX standard AFM's and ECU's, I got no idea where to start sorry mate. We don't experiment with those things over here, it's either standard GTX gear or it's full aftermarket.

I'd be checking things like fuel filter and also the possible addition of a rising rate fuel pressure reg.

[jitb37]

Aside from the starting issues I am having with the GTX, I also encountered another strange issue. Yesterday I drove it pretty hard up a hill. At the end of the hill, I slowed down but I was still in a high gear. I believe I was in 4th and doing 35 mph. I step on the gas a little and the car bogs down and lurches forward in a really weird fashion - so I slow down some more and crawl to a stop. My EGT's while going up the hill did not go over 1150F. I stopped the car and let it idle and cool down. I then started driving again and drove just fine - pulled like before and did not bog down.

What could have hapenned? I am running the NA ECU at stock boost with GTX injectors, an RX7 VAF and a Walbro fuel pump. Could that bogging down be running lean - why would it run lean at part throttle and low RPM? My car smells really rich at idle. Could it be overheating? My EGTs do not seem extreme and my temp gauge was not out of the ordinary.

Later that night I pulled the plugs and valve cover. The plugs looked ok (although a little too white) and everything looked well inside the valve cover.

If I am running lean and detonating, is the bogging down a result of it? How can I tell if I detonated? (are there any signs on the engine that are easily visible) I hear no pinging from the engine even under load at a low RPM in a high gear.

Some input from you turbo experts would be great. Thanks.

Might want to check that distributor....might be dieng. Exact same thing happen to me.

[elscotto80]

Prolly just a hickup. When my tank gets to 4 gallons left, the sutupid walbro wont pick up anymore fuel and bogs. I think I installed the wrong sock, but meh, I can live with re-fueling sooner than I did when I was n/a.

[jitb37]

Prolly just a hickup. When my tank gets to 4 gallons left, the sutupid walbro wont pick up anymore fuel and bogs. I think I installed the wrong sock, but meh, I can live with re-fueling sooner than I did when I was n/a.

thats true..that would happen to my friend when he had the rx7 TT pump..

And happen to me when i installed the fuel pump, and folded the screen on accident...

[Lex]

Yeah it def seemed like a hickup - I just never had those with my NA setup before. The weird thing is that it happenned when I was not revving high, in a high gear and not really loading the engine ...

jitb, you had the same problem? Can you describe it to me ... was it the distributor itself or just the cap/rotor?

It might be the pump as well - at the time my low fuel light was on

Man, I got 250km on a tank of 94 since I went turbo! That is really crappy fuel economy!

[jitb37]

I would be driving, ..and all of a sudden, the car would loose all power, and sudenly get it back. And it happened everytime i made right hand turn. And it was the distributor, b/c i replaced the cap/rotor last year when i did the piston rings and al lthat. i grabebd one from the pullapart from a EGT (go figure). There pretty expensive i think 180$ for a new one.

I thought it was the fuel pump, so i bought one..(160$) and replaced b/c the car actually died on me on the HWY. But i replaced the disty and it cranked up. A week or so before it completly died, it would keep doing that and it just got mor eand more common, until it just died.

[Lex]

I was doing a right hand turn as well when it happenned ... maybe it was just that. I have the distributor off my NA engine and I can always put that in if the GTX one goes

That is some really good info - thanks a lot

[JordyB]

Thats a low/part throttle - high boost/load symptom using the EGT ECU...not enough fuel for the load/boost levels your turbo wanted to be at...and the ECU never knew about. Imagine a 3" turbo back and 2.5" piped i/c and letting her breeth, boost comes on even sooner and the ecu doesnt know it needs to give fuel because its not programmed in the maps for it...

Your right hand turn coulda been the 1/2 tank or lower fuel slosh problems alot of the EGT's have like mine...

[Lex]

Jordy, were you also running the EGT ECU for a while?

Althought my exhaust is stock (with the GTX downpipe), my intake is all 2.5' mandrel bent.

How dongerous is this condition?

[jitb37]

I was doing a right hand turn as well when it happenned ... maybe it was just that. I have the distributor off my NA engine and I can always put that in if the GTX one goes

That is some really good info - thanks a lot

if its doing it when u make right turns, like mine was. Than thats it. ti will get worse and worse. And start doing it when at high speeds. Keep that mofo in your trunk...and a 12Mm socket just in case...lol

Did it ever backfire? when it did this?

That fuel slosh thing was an issue with me aswell. but like i said before, i had folded the fuel pump screen, by accident when i installed it.