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View Full Version : Surging at WOT


Survivor87
03-10-2006, 07:29 PM
This has been ongoing, but I have been correcting some other problems (oil leaks, header leaks, etc.) before tackling this. Car runs decent, especially in the part throttle range, but often at WOT it will lay down momentarily and then come back on fairly strong, but not as you would expect. I swear sometimes it feels like it's pulling harder at about 3/4 throttle. BLM readings are staying in the upper 130's, no knock detected, MAF showing 255 at WOT. Has hot wired Walbro 340. Have moved the FP up and down a bit, but no change in symptoms. Does it with the stock chip and one of Conley's pump gas chips (Mini- Mag). Any ideas where I need to start looking?

JHensberry
03-10-2006, 07:31 PM
what is the status of your coil pack/ignition module/plug wires?

Survivor87
03-10-2006, 09:38 PM
I believe the coil pack has been replaced recently......not sure how to check it? New wires: MSD . Ignition module: not a clue.

JHensberry
03-10-2006, 10:04 PM
You can check your coil pack, per website/quick ref. by using a multimeter across each post on the 3 towers.

You should see generally 11-13KOhm of resistance across each tower, the higher the better.

Also I hear the Caspers Coil Pack/ignition module tester is very good if you have access to one of those.

Not leaning towards fuel issue, but do you have a hood mounted TestNTune FP gauge to make sure the FP goes up accordingly with each pound of boost?

Survivor87
03-10-2006, 10:55 PM
I will check the coil pack tomorrow as you suggested and report back. I do have a remote fuel guage, have not installed yet. I have a Bosch "237" regulator, if that makes any difference. Could something be going on with the wastegate or wastegate solenoid? Thanks for the reply.
Steve

JHensberry
03-10-2006, 11:28 PM
Normally, a defectice solenoid or wastegate will result in overboost.
How much boost at the WOT problem area?
The BLM of upper 130s says it is a little lean, but the intergrator should take care of that for you.
I'm still kinda leaning toward a weak coil pack or failing ignition module. HTH, Joseph.

kenmosher
03-11-2006, 11:10 AM
What are your O2s when it does this?

JHensberry
03-11-2006, 08:54 PM
Sorry, did not even think about that..... :duh:

Survivor87
03-12-2006, 08:53 AM
Got busy checking out a parts car yesterday and didn't get back on the GN till last night. The coil pack ohmed out OK (12.4-12.7K) I still need to get that f/p guage situated where I can read it while driving. I didn't think about the O2 readings either....I'll get back out and get some numbers later today. Heading to the track this morning with my "Brand X" car. Don't give up on me yet!

Survivor87
03-13-2006, 09:53 PM
Okay, I have some more input on this problem........and possibly questions for another thread. Discovered after a couple short hard passes that it was making way too much boost. It was taking quite a bit of timing out, so I started adjusting back on the boost, which helped with the retard readings, but the pressure seems to be very erratic. It will flash to 13-15 psi upon stabbing the throttle then back down some and then come back even higher. This is after backing off 6-8 turns on the adjustment (1 or 2 turns at a time). I had just re-welded the d/s exhaust header, so I was wondering if this had caused the big increase in boost pressure. Through all this testing (about four short sessions of backing off the boost), minimum O2s stayed in the 820-860 range and f/p is rising as it should with manifold pressure. So what do I need to do next?

Keller
03-13-2006, 11:53 PM
I had just re-welded the d/s exhaust header, so I was wondering if this had caused the big increase in boost pressure.
Yes, that definitely could have. Its sounds like it was MUCH higher. Like almost-gonna-pop-a-headgasket high.

I would check the condition of the wastegate hoses, the orientation of the "Y", and the connection of the wastegate solenoid. If all of that is good, then I would give the car a good one over with a scan tool. The fuel pressure might be a hair high for max power, but I would not want to lean things out until the boost control was more stable. Perhaps your wastegate hole in the turbo needs porting, etc. to stabilize boost control. Is your fuel pump and such all up to snuff?

Survivor87
03-14-2006, 09:17 AM
Yeah, the boost was approaching 19-20 momentarily when I first started testing which was alarming to say the least. I was lifting pretty quick those first couple of tests (shortly after 1-2 shift). I did get some audible knock but I don't think I hurt anything. I've owned the car for a year now and this is probably as hard as I've ever driven it because I wanted to get some of these other little mechanical things fixed first. It's possible the previous owner had the boost set too high when I got the car; it's just hard to believe that little crack in the exhaust manifold could make that much difference. I will double check "Y" orientation, the hoses, and solenoid connection. I am pretty confident in the fuel system; pump is new and pressure was responding good with the boost. What about the actuator itself? Do these things fail often and if so would it cause such erratic readings? I would think if it failed there would be no pulling back at all of the boost, and it does seem to be doing that, albeit unpredictably. Thanks for the advice.
Steve

Keller
03-14-2006, 01:34 PM
I did get some audible knock but I don't think I hurt anything.
Audible knock is pretty big knock.

What chip are you running?

Survivor87
03-14-2006, 01:55 PM
It is one that I got from a friend...pretty knowledgable and conservative TR owner. All I know is it says "Mini Mag" on the back. He said it was one of Conley's pump gas chips. Have you heard of it?

Keller
03-14-2006, 03:36 PM
Heard of it. Not sure if that profile has been updated in some time. You'd probably have to check with Conley. And then the question is what version do you have. Some of the more recent designs might offer better control of fueling and boost. Many are using newer designs from TurboTweak, Jay Carter, Red Armstrong, etc.

Survivor87
03-14-2006, 07:06 PM
I do have a recent chip in my hands ready to go ( from fullthrottlespeed). But it is set up for my new injectors and turbo which are not on the car yet. I'm trying to do the "get it running right in stock trim" thing before I put any of this stuff on. Car behaves the same with the stock chip. Now that I have the boost down to a sane level, I took it out once more. It seems pretty decent at part throttle but as soon as you get enough foot in it to make the Scanmaster go into record mode, it will really come on strong and then just kind of lay down. It comes back somewhat but not like before. And it's not pulling timing out now, at least according to the Scanmaster. I thought maybe that was the cause before (when it was overboosting).

Keller
03-15-2006, 03:15 AM
Can you see the Block Learn, Integrator, and MAF numbers both at Full and 3/4 throttle and see what they look like?

Survivor87
03-15-2006, 08:58 AM
I'll try to get out today and do that. It might take six pulls or more to get all of that........are you looking for a fuel system problem?

Survivor87
03-15-2006, 09:39 AM
Have to leave town for a few days, so I will be offline for a while. When I get more info I'll post it up. Thanks,
Steve

Survivor87
03-22-2006, 05:03 PM
Okay, I put the stock chip back in it and went out to do some tests today. Part throttle was giving me a MAF reading of about 220-250 gps and the integrator and BLM readings seemed to stay right around 128. Same at WOT except for MAF was reading 254 gps. Surging is worse at WOT but I can detect some at part throttle as well. It seems the only thing that moves when this happens is the boost pressure.
So.....groping for answers, I went to the service manual. Followed the flow chart for electrical diagnosis of the W/G solenoid. Now even though it is not putting up code 31, the very first test came up with voltage accross the the connector which supposedly points to either a defective ECM or a short to ground on circuit 928, which looks to be OK as far as I can see. Am I on to something? I'm a liitle perplexed because it isn't throwing a code.

Keller
03-23-2006, 11:03 PM
One quick way to see if its the solenoid or something else is to just run a single hose from the wastegate to the compressor hose fitting. Bypass all the other stuff: the "Y". the solenoid, etc. You'll only get about 12 PSI, but it should be rock-solid. If not, the actuator might be bad. Or, it could be a fueling problem.

Survivor87
03-24-2006, 08:45 AM
OK, thanks. I'll give that a try. I'm still wondering about that solenoid. If I can get my hands on another ECM I'm going to plug it in and see if it shows a different result.