Check Engine light & poor driveability

[Wraythe]

Fellow Syclone & Typhoon brothers,

I purchased my Syclone from the 2nd owner with 75,xxx miles in southern California a few months ago. The moment I test drove the Syclone I knew it had a driveability issue however this did not stop me from making the purchase.

After being on the Interstate for approximately 60 minutes, the check engine light illuminated and it drove poorly with boost gauge showing positive boost. I pulled over at the next exit, reviewed the owners manual and checked everything over on the Syclone. Upon starting the Syclone, I noticed the Check Engine light was off and continued my trip home. About 30 minutes latter, the Check Engine light illuminated again and it drove poorly with boost gauge showing positive boost. I made the decided to continue driving the Syclone and reduced traveling speeds. About 90 minutes latter, the Check Engine light turn off and the Syclone drove well again :rant:

My question to the community is:
1. How should I troubleshooting this issue?
2. Should I purchase a scanner or will the on-board diagnostic toot be fine?
3. Any other suggestions?

Sorry for looooooong post. Any suggests would be greatly appreciated :tup:


FYI - Upon purchasing the Syclone, the prior owner had a tune-up (plugs, wires, cap, rotor) completed which I have the receipt.

 

[JAY]

Re: Check Engine light & poor driveability

Yes, a scan tool of some sort should be your first step. What fuel are you running? These trucks hate low grade premium. Where is the timing set? Vacuum lines around MAP sensor or fp regulator. Cat conv plugged. It could be any number of things.

 

[Wraythe]

Re: Check Engine light & poor driveability

Yes, a scan tool of some sort should be your first step. What fuel are you running? These trucks hate low grade premium. Where is the timing set? Vacuum lines around MAP sensor or fp regulator. Any number of things.

What scan tool does the Sy/Ty community use? Is it best to purchase a cable to interface from my laptop to my Syclone or should a standalone scanner?

I only use "Premium - 91 Octane " fuel in my turbo vehicles.

I have not verified timing but I will this evening

Considering this is 1991 and stock, I better replace ALL vacuum lines. I don't see or hear any vacuum noise currently.

Where is the best place to order replacement vacuum lines from and what's the size?

Thank you sooooo much for the reply :tup:

 

[MICH TY]

Re: Check Engine light & poor driveability

Where is the best place to order replacement vacuum lines from and what's the size?

Thank you sooooo much for the reply :tup:

Sportmachines has a vac line kit for our trucks
http://sportmachines.net/products/

 

[coupecustom]

Re: Check Engine light & poor driveability

After reading your post my first thought was vacuum lines too. When I replaced all mine I got a silicone hose kit from Sport Machines. They'll include instructions and a diagram, so it should be very easy for you to do.

91 is a little low, but your in California, so I guess that's all you can do. :-(

 

[powercat6]

Re: Check Engine light & poor driveability

Since you don't have an ALDL cord yet; you can use a bent paperclip to retrieve codes.

http://www.sportmachines.com/wiki/article13-Assembly-Line-Data-Link-ALDL-Information

 

[Wraythe]

Re: Check Engine light & poor driveability

Sportmachines has a vac line kit for our trucks
http://sportmachines.net/products/

Thank you!!! I was told the shop was closed for a funeral

 

[Wraythe]

Re: Check Engine light & poor driveability

After reading your post my first thought was vacuum lines too. When I replaced all mine I got a silicone hose kit from Sport Machines. They'll include instructions and a diagram, so it should be very easy for you to do.

91 is a little low, but your in California, so I guess that's all you can do. :-(

I'm located in Salt Lake City, Utah (aka The SLC)

Thank you for the reply!!!! Lots of love here

 

[Wraythe]

Re: Check Engine light & poor driveability

Since you don't have an ALDL cord yet; you can use a bent paperclip to retrieve codes.

http://www.sportmachines.com/wiki/article13-Assembly-Line-Data-Link-ALDL-Information

I'm keeping my Syclone stock should I still invest in purchasing an ALDL cable?

Thank you for the reply!

 

[Quickstop [UK]]

Re: Check Engine light & poor driveability

A Moates Extreme ALDL is the best cable I have found but before you throw a tonne of money, what is the paperclip telling you?

It flashes each sequence 3 times before moving to the next code...

 

[Wraythe]

Re: Check Engine light & poor driveability

A Moates Extreme ALDL is the best cable I have found but before you throw an tonne of money, what is the paperclip telling you?

It flashes each sequence 3 times before moving to the next code...

I'm currently at the office but I'm planning to use the paperclip method this evening. I'll post my findings

 

[JAY]

Re: Check Engine light & poor driveability

When you check the timing make sure that you disconnect the wire under the heater box under the carpet.
http://www.syty.net/forums/showthread.php?t=32006&highlight=base+timing+set

A good write up here:
http://www.syty.net/forums/showthread.php?t=92348&highlight=base+timing

Purchase one of these manuals:
http://www.ebay.com/itm/1991-GMC-Tr...anuals_Literature&hash=item20e0813c7d&vxp=mtr

Concerning octane, just because you're paying for 91 doesn't mean that's what you're getting. I've seen news reports where they tested some 91 that was actually 85. I use FPF octane boost every time I fuel the Syclone.
http://www.fppf.com/products-by-name?task=catalog.product&id=33

 

[Wraythe]

Re: Check Engine light & poor driveability

When you check the timing make sure that you disconnect the wire under the heater box under the carpet.
http://www.syty.net/forums/showthread.php?t=32006&highlight=base+timing+set

A good write up here:
http://www.syty.net/forums/showthread.php?t=92348&highlight=base+timing

Purchase one of these manuals:
http://www.ebay.com/itm/1991-GMC-Tr...anuals_Literature&hash=item20e0813c7d&vxp=mtr

I'm so happy you mention to disconnect the wire under the heater box and thank you for hyperlinks!

I noticed SportMachine has a compiled DVD with all the Syclone service manuals. Would the DVD be a better solution?

 

[Wraythe]

Re: Check Engine light & poor driveability

Concerning octane, just because you're paying for 91 doesn't mean that's what you're getting. I've seen news reports where they tested some 91 that was actually 85. I use FPF octane boost every time I fuel the Syclone.
http://www.fppf.com/products-by-name?task=catalog.product&id=33

Damn! Is everyone doing this for their fuel ups

 

[JAY]

Re: Check Engine light & poor driveability

I'm so happy you mention to disconnect the wire under the heater box and thank you for hyperlinks!

I noticed SportMachine has a compiled DVD with all the Syclone service manuals. Would the DVD be a better solution?

It's up to you. If you're already buying a hose kit, might as well save shipping with the manuals & support a company that supports us!

If you can find pure premium gas w/o the R/M rating on it, you'll notice a difference. I miss the 93 octane we had in Houston.

 

[berzerker]

Re: Check Engine light & poor driveability

i'm gonna go out on a hunch and say it will have egr codes stored . Do you know if the stock memcal is in the ecm or aftermarket ? let us know what you can about any modifications the previous owner may have done.

 

[IGottaSy]

Re: Check Engine light & poor driveability

O2 sensor

 

[Wraythe]

Re: Check Engine light & poor driveability

Fellow Sy/Ty Comrades:

I'm completely shocked it's May! My beloved Syclone has been sitting in my garage untouched since my last post. Due to work, family and other activities I've had no time to troubleshoot the issue until today. I want to thank everyone who posted to this thread and instant messaged me!!! It has been greatly appreciated

The following are general questions I have been asked:

1. I believe my Syclone is stock however how can I verify if my chip is OEM?
2. Getting code 32 from the ALDL Diagnostics Connector which is an issue with EGR circuit

Any suggestions what my next step should be?

Thank you!!!

 

[Wraythe]

Re: Check Engine light & poor driveability

I just noticed someone had posted SportMachines.com as a reference for ALDL codes. As per SportMachines:

Vacuum switch shortened to ground on start-up, switch not closed after the ECM has commanded the EGR for a specified period of time or the EGR solenoid circuit is open for a specified period of time. Replace the EGR valve.

Looks like I'm replacing the EGR valve today. I'll provide an update once I replace the EGR valve

 

[SY2455]

Re: Check Engine light & poor driveability

Concerning octane, just because you're paying for 91 doesn't mean that's what you're getting. I've seen news reports where they tested some 91 that was actually 85. I use FPF octane boost every time I fuel the Syclone.
http://www.fppf.com/products-by-name?task=catalog.product&id=33

I don't know Jay if I would use that one after checking the link out because you can buy it in a 12 oz. bottle that treats 30 gallons or you can buy it in a 55 gallon drum that will only treat 2 gallons. I'm not taking the chance with that one :rotf: :rotf::rotf:.

Here in California to deal with the 91 octane gas I have been adding a bottle of Lucas "A real octane booster" and the truck sure seems to like it.