I've got a stock '87 L98 4+3 automatic that I'm experiencing rough idle, labored acceleration in 4th gear at highway speeds, and drastic detonation/preignition under acceleration load at full throttle.

I've applied many different chemical injector cleaners, including fuel-additives, and vacuum-system products. Each helps out a little bit up to a point, but after a tank or two without additive, I'm right back where I started from.

So, I've more-or-less narrowed it down to the injectors. I've got two choices from what I can see. I remove the injectors myself and ship them off to Lingenfelter for $80 or cruzinperformance for $11/injector. Takes my car down for about a week. Or, I can take it to a local shop who will do what they call a "reverse sonic cleaning" which apparently does a sonic cleaning without removing the injectors. This will cost me $39/injector.

All things being equal, does anyone have any experience with this "reverse sonic cleaning?" Will it work as well as a full removal and cleaning?

My concerns are having to rent a car for the week my 'vette will be down, and the technical aspect of having to remove and replace the injectors myself (I've never done it myself, and I see that it was a pain even for guys from this forum with lots of experience.)

Any advice will be appreciated. Also, is there a place I can easily obtain instructions for the removal of the injectors, say from the internet, or should I just go buy a Chilton, or Hames manual?

Thanks in advance,
Rob

 

Reverse cleaning is not going to fix it if an injector or more is bad. If your 87 has not been touched, it has bosch injectors, which are not the greatest. Pull the plugs off your injectors and measure the resistance across the two connectors, write em down and see what you got, each one should read 16-17 ohlms. Any more or less would indicate an operational problem with the injector itself which cleaning won't fix. It was recomended by Gordon Kilabrew, (C4 tech manual writer and chief C4 mechanic) to use Taylor injectors (don't remember the part number) in place of the Bosch. He also is where the above procedure came from. Start there before you spend a bunch of money on things that may not work. Hope this helps :cheers:

 

I am not totally sure it the injectors problem. But on the subject of removing injectors, you can do it yourself. Just a matter of taking the plenum, runner off to get to the injectors. Just make sure you pull the fuel pump fuse off and run the car until there are no more gasoline in the fuel rail and get some plug to plug off the fuel line at the front of the engine. I am not an expert on any engine by any means, but I have taken the plenum and runner out three times so it seem easy to me now.

 

As a suggestion you might consider calling Rich @ cruzin performance. He will answer all your questions. In addition, he might have a set that will fit your car from his stock. A very nice guy.

 

For what it's worth, I was not happy w/ the "injector job" that Lingin did to me.

To get the injectors out of an 87, it can be involved, but it is nothing too difficult or complicated. A couple points to remember. These are ALU parts. Don't tighten the shot outta them when you are putting them back together. Lube the injector seals when seating the rail, so you don't tear a seal.

In a nutshell:
Remove 4 bolts holding TBody-> plenum (May tear gasket, let Tbody dangle)
Pull the Plenum (If you are good you won't tear a gasket)
Loosen/Pull the V covers, (Alt may get in the way, start w/ pass side)
Pull the runners (Again, Start w/ Pass side, may only need to take one side off)
Pull the fuel rail
Rotate clip to remove injector from rail

 

Here's what Rich at Cruizin posted a while ago which I saved to disk. I haven't had time to poke through the forum archives to find the link again yet. According to Rich the 87 injectors are pretty good. :D

Shadow2
rich@cruzinperformance.com
Member
Posts: 1
From: Michigan
Registered: Feb 2000
posted 04-23-2001 10:44 PM
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I don't get a chance to visit here often but please allow me to shed some light on this subject.
The early multi-port injectors used on the Corvettes were manufactured by Bosch and some by Rochester Products. These were some of the best injectors ever produced. I have customers with well over 100K miles on them and they are functioning as good as they did when they were new.
The injectors used on the 85 model year(#5235041)have a slightly higher flow rate due to the fact that GM set the fuel pressure regulator at 37psi rather than at the 42psi that the later models had. Both the 85 and 86 model year(#5235211)used plastic pintle caps that can get brittle with age and sometimes crack and come off the injector when the rail is lifted. These are easily repaired by simply installing new pintle caps.

The 87-88 model years used an injector manufactured by Rochester Products (#5235302)and feature a stainless steel pintle cap that is swedged onto the injector and will not crack or fall off.

In 1989, GM introduced the first design Multec injector(#17086544 and #17086545). These injectors are easily identified by their Gray plastic main body. With this new design, fuel was allowed to come in contact with and flow around the solenoid coils to "cool" the windings of the coils. Herein lies the problem that has been the downfall of these injectors. Some oxygenated fuel blends and various "chemical injector cleaners" attacked the insulation coating of the windings and caused the windings to "short out". When this happens, the injector starts to become a "low impendance injector" and the dwell time of the injector increases. The result is a richer fuel mixture than is desired. A quick check with an ohm meter will determine whether the windings insulation is intact or if it has been degraded. If the insulation has degraded there is no simple repair for the injector and it needs to be replaced.
In defense of Rochester Products, the second design Multec injectors (Black plastic body) that were installed on the LT1's and LT4's were re-designed and don't exhibit the problems of the earlier Multecs.

The use of adjustable fuel pressure regulators ultimately depends on the amount of tuning and tinkering the owner wants to do to his engine. If you want to "fine tune" the engine and you have access to either a diagnostic scanner to capture O2 data or if you want to adjust the pressure at the drag strip where you can duplicate the conditions run after run then they can be a useful tool. Accel, BBK, and Holley all offer quality regulators featuring a billet cover and all come with a new diaphragm.

Sorry this was so long but I felt it necessary to get this information out in the open and it's kind of hard to condense. Email me if you have additional questions and I'll try to answer asap.

Lastly.. Thanks 65Z01 and Muffin for the kind words. I appreciate your support

Rich @ Cruzin Performance (aka Shadow2)

 

Have you checked or condsidered plugs and plug wires..
Your symptons could be that simple to correct

 

Stock87,

It is my opinion that replacing the injectors on your 87 will be a bit more hassle than some would have you believe. You can do it however. It doesn't require a lot of mechanical knowledge, just patience. And a few extra tools.

The 89 and later vettes are a lot easier than the 85 - 88. There is a 9th injector on the 85 - 88 vettes that was removed on 89 and later. This injector (called the cold start valve "CSV" by GM) and its separate fuel line is a PIA to deal with due to physical placement. The key here is to go to the tool store and buy a set of flare nut wrenches. You can get a set at Pep Boys or NAPA or other stores easily for under $20. I bought a cheap set from NAPA which had sizes from 11/16 to 3/8". The 11/16 and 5/8 size are the most critical. The 11/16 will fit the main fuel rail inlet connections as well as the driver side plenum nut. The CSV fuel line nut is either 11/16 or 5/8. having the flare nut wrenches makes this a LOT easier. Buy them before you start. These wrenches make replacing the fuel filter a breeze too.

Two other good tools to have on hand are a telescoping magnetic pickup tool (about $2) and a 4" - 6" T40 Torx extention (available from MAC, Snap-on etc. about $12 - $25 depending). The torx extention is really a time saver when getting at the lower plenum bolts.

If you wanted avoid downtime and save money I'd recommend that you consider buying Ford Motorsport 24# injectors and doing it yourself. If you have the injectors, a complete set of gaskets, and the tools all ready to go, you should be able easily to do it yourself in one day. Having someone else to help will move things along a lot faster of course.

To avoid time consuming problems I'd buy the tools I've already mentioned as well as gaskets for the throttle body, the runners, and get 2 new o-rings for the fuel rails and the CSV rail. That way you are covered if some gasket gets torn. Besides it doesn't cost that much to replace the old with new.

Although not absolutely necessary you might consider getting a rebuilt CSV from Rich at Cruisin Performance. Also, if the EGR is original, I'd consider getting a new one. Be sure to buy an AC-Delco factory replacement. All of the aftermarket replacements require some minor mods. I checked everywhere. The GM unit is about $35 at the dealer and mine came with a gasket in the box. Buy all your gaskets and EGR parts from Jeff Koop 800-728-8267. You will get original GM parts that fit perfectly at discount prices.

For easily under $300 and one Saturdays effort you will have a whole new engine. It will run so smooth you'll swear something is wrong. The savings from not renting a car for a week will pay for the new injectors. Save the old ones and have Rich rebuild them for future use when you have the cash.