engine surges at high rpm WOT. help!

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boominrick
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engine surges at high rpm WOT. help!

Post by boominrick » Sat Nov 15, 2008 10:26 am

I have a 89 XR4Ti 5 spd. and when im getting on it around 4k the motor surges, i can hear the turbo spooling but it feels like i let off the gas. sometimes it gets better but most of the time i just let off.

mods done to the car are, LA3 with big VAM and a rapido fmic.


i checked the TPS yesterday and it was loose, just floating around. so i set it to .93 volts at idle.
idle control valve is ok.
fuel pressure is 35-40 psi
boost control solinoid is disconected and bypassed to 15 psi
egr is disconected and pluged
compression back to front is 120 110 120 110

key on engine off codes are 81 82 83 84

engine running codes are 34 74 77


i was thinking about checking the cam timing and ignition timing today and maybe even change the timing belt and TFI




anyone have some imput?
89 xr4ti

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John R. Rowlands
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Post by John R. Rowlands » Sun Nov 16, 2008 12:45 am

boominrick,

Code 84 and 34 are EGR codes. 81,82 and 83 are thermactor codes you don't have a thermactor. All these odd codes are caused by the LA3 ECU.
Code 77 is a dynamic response code meaning you didn't blip the throttle correctly when running the KOER test. Code 74 is the BOO test, brake on and off, another LA3 code.
Suggest you check all your grounds the primary one is the one that runs from the battery negative to the bottom of the battery box.
Take it one step at a time.

John
If it ain't broke don't fix it!

BeefFajitas
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Post by BeefFajitas » Sun Nov 16, 2008 9:56 am

Unplug the KS?
-Nate
'85 Merk. Back together. Only thing stock is the head and block.

86XR4Ti_John
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Post by 86XR4Ti_John » Sun Nov 16, 2008 11:32 am

codes aside, I suspect a boost leak that isn't evident in vacuum or with the engine off.

You will need to pressurize your intake tract with some compressed air. You can make a boost leak tester quite cheaply.

You need a rubber/silicone fitting that goes over the turbo intlet, and a short piece of plumbing pipe that fits into the rubber. Then you need a cap to go on the other end. Then you put a tire air valve stem in the cap. Put the thing togeather with some of the correct glue(Either for PVC or whatever kind of plastic you use). Clamp it onto the turbo. Put compressed air to it.

Use an air compressor, bike pump won't do it unless all your intake valves are closed.

Pressure it up to 15-20 psi. Find the leaks, large and small.

Yours sounds large tho, so its probably one of the couplers on the intercooler plumbing or a hole in a pipe.
John

86 Xr, lowered, cossie rear sway bar, wheels, intercooled, big vam, PE superchip.
91 Talon TSi, well modified, 5spd all wheel drive, runs 11's.

boominrick
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Post by boominrick » Mon Nov 17, 2008 7:24 am

I will try everything said above, I changed the timing belt yesterday and the cam timing was off 2 teeth. So I put a new one on and corrected it. Took it for a ride and it was a lot better. Only surged once in about 10 runs. I might try bringing the timing from 13 btdc to 10. Also it seems now like past 4k it's slow to climb rpm's. I blew a coolant hose so after I fix that and change timing I'll let you know

boominrick
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Post by boominrick » Fri Jan 30, 2009 6:28 pm

i am still having this surging problem.


i pressure tested the intake today. only gave it about 10- 15 pounds and i have a pretty big leak at the stock boost solinoid. it actualy blows it out of the p;lasic bowl it sits in.


i tried holding it down and it came through the dipstick.


i realy want to fix these problems



also at idle the car has about 10lbs of vac. and i would say about 13lb on deceleration.



i went to NAPA and bought some brass fittings to make a check valve but i canot find a ball bearing. no auto parts have them and lowes does not have them.


i need a alternative to vent the crankcase i beleive.



i also went to a dyno shop and asked what they do with the pcv/check valve and they told me they cap the inlet on the intake and just let the breather vent to atmosphere.

is that safe? or should i run some sort of pump?
89 xr4ti

hEaT
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Post by hEaT » Fri Jan 30, 2009 8:18 pm

boominrick wrote: i also went to a dyno shop and asked what they do with the pcv/check valve and they told me they cap the inlet on the intake and just let the breather vent to atmosphere.

is that safe? or should i run some sort of pump?
Go get a FORD PCV valve for an SVO Mustang. Parts store metal ones are trash. It should only pass air one way. If it passes both ways, it's trash.

You can replace the stock BCS and install a manual boost controller. www.boostvalve.com is a good, cheap one. Set it at 15psi unless you have an intercooler. You can also just bypass it for the timing being, but you'll be limited to ~10psi.
Joe
1985 Nimbus Grey XR
2017 Ford Focus RS

boominrick
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Post by boominrick » Fri Jan 30, 2009 9:17 pm

Also it has a weird idle, if you let it sit and idle, say the drive through it will all of a sudden get real rough like it's firing on 2 cylinders, then after it changes it's tampon about 2 minutes latter it reves to about 1500-2000 Rpms and drops down to 1000.


Another thing it does that aggravates the hell out of me

When I'm driving and say I'm coming to a red light and I put the clutch in the rpms will drop down to 500 or lower and climb back up to 1000, sometimes it would stall so I will let clutch back out to pop start it. Very aggravating
89 xr4ti

onebadazzsrt
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Post by onebadazzsrt » Fri Jan 30, 2009 9:59 pm

Thats why I'm gonna do a 302 swap, turn key and go.
J

1987 xr with rs500 fiberglass wing,outcast grill,new shoes,5.0 with GT40 package,powerdyne blower 9psi kit,255

Scalawagk9
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Post by Scalawagk9 » Fri Jan 30, 2009 10:05 pm

boominrick wrote:Also it has a weird idle, if you let it sit and idle, say the drive through it will all of a sudden get real rough like it's firing on 2 cylinders, then after it changes it's tampon about 2 minutes latter it reves to about 1500-2000 Rpms and drops down to 1000.


Another thing it does that aggravates the hell out of me

When I'm driving and say I'm coming to a red light and I put the clutch in the rpms will drop down to 500 or lower and climb back up to 1000, sometimes it would stall so I will let clutch back out to pop start it. Very aggravating
Ditto here. And I'll add that the dipping, sometimes stalling, idle problem is only when the engine is hot. It can intermittently stick at around 2K at times, but usually drops if I blip the gas pedal. I'm thinking my issues are both leaking vacuum (somewhere) and probably a dirty idle air control. After cleaning the IAC, I'll try resetting the TPS and idle. Any other ideas?

hEaT
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Post by hEaT » Fri Jan 30, 2009 10:17 pm

Yeah, try resetting the idle per these instructions:

http://www.turbotbird.com/techinfo/Idle ... e2005.html
Joe
1985 Nimbus Grey XR
2017 Ford Focus RS

Scalawagk9
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Post by Scalawagk9 » Fri Jan 30, 2009 11:24 pm

Thanks hEat. That link makes the procedure clear. I knew I had to backpin the connector but was unclear as to which wires.

Part of my erratic idle was definitely vacuum leaks. The brake booster (used) and PCV (Motorcraft) were replaced today, and I can already see an improvement in the idle. I got a chance to drive for the first time between my first post and this post, and the idle seems to be staying steady at least in the short drive I had on a cold engine. I'll set the idle and adjust the TPS tomorrow.

hEaT
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Post by hEaT » Sat Jan 31, 2009 9:42 am

Good to hear. Glad I could help.
Joe
1985 Nimbus Grey XR
2017 Ford Focus RS

boominrick
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Post by boominrick » Sat Jan 31, 2009 12:19 pm

I will do the idle again today, I think before when I did it I adjusted the tps after I pluged the IAC back in.


Any idea what the surging might be?

When it happens if I let off and have it at around half throttle it will stop the surging and start moving again
89 xr4ti

boominrick
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Post by boominrick » Sat Jan 31, 2009 4:56 pm

Boost controler is all set, I made one today and set it to 15 pounds, the old BCS is hooked back up to the computer.

I tried making a check valve but it didn't work so well. The ford dealer told me the svo pcv valve is discontinued. So what do I do? And also can I put a. Check valve to the supply to the vacuum tee?

I really need to fix this surging problem!
89 xr4ti

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